When scientists dream of exploring the hidden oceans beneath the icy crusts of moons like Jupiter's Europa or Saturn's Enceladus — or other icy regions, such as permanently shadowed lunar craters or ice-bearing soils near the Martian poles — one major problem stands in the way: drilling through the ice.

Traditional drills and melting probes are heavy, complex and consume vast amounts of power. Now, researchers at the Institute of Aerospace Engineering at Technische Universität Dresden in Germany have developed a promising new solution — a laser-based ice drill that can bore deep, narrow channels into ice while keeping both mass and energy requirements low.

"We've created a laser drill that enables deep, narrow and energy-efficient access to ice without increasing instrument mass — something mechanical drills and melting probes cannot achieve," Martin Koßagk, lead author of the study, told Space.com in an email.

Mechanical drills become heavier with depth as they extend rods downward, and melting probes rely on long, power-hungry cables. The laser drill sidesteps both problems by keeping all instruments at the surface. This tech sends a concentrated beam into the ice, vaporizing it rather than melting it — a process known as sublimation.

The resulting vapor escapes upward through a narrow borehole just wide enough for gas and dust samples to be collected. Instruments on the surface can then analyze these samples for chemical composition and density, providing valuable clues about the thermal properties and formation history of the cosmic body being explored.

While lasers aren't the most energy-efficient tools, the beam vaporizes a mere pinhole of ice, meaning the drill uses far less total power than electric heaters. It also works faster in dust-rich layers that slow traditional melting probes, allowing it to bore much deeper without added mass or energy.

Therefore, a laser-based instrument "makes subsurface exploration of icy moons more realistic, allowing high-resolution analysis of ice composition and density, improving models of heat transport and ocean depth on bodies like Europa and Enceladus, and supporting studies of crust formation," Koßagk said. "On the moon or Mars, the laser drill can also extract subsurface material such as dust from ice-bearing craters or soils, enabling geological reconstruction beyond the surface layers."

The team's laser drill concept operates at roughly 150 watts (W), with a projected mass of about 9 pounds (4 kilograms), remaining constant regardless of depth — whether 33 feet (10 meters) or 6 miles (10 kilometers). However, Koßagk noted that a mass spectrometer for analyzing the gas and instruments for dust separation and analysis would increase the power requirement and mass.

Early tests show promise. The prototype drilled through ice samples about 8 inches (20 centimeters) long under vacuum and cryogenic conditions during laboratory experiments, and at greater depths in field tests in the Alps and Arctic, reaching depths of more than a meter in snow. In tests with 20 watts of laser power, the system reached drilling speeds near 1 meter per hour, and up to 3 meters per hour in loose or dusty ice.

A laser-based concept is not without limitations. In stone or layers of dust in which there is no ice that could be vaporized, the drilling process would be stopped. And, in those cases, a new borehole would need to be drilled from the surface that bypasses the obstacle.

"It is therefore important to operate the laser drill in conjunction with other measuring instruments," Koßagk told Space.com. "Radar instruments could look into the ice and locate larger obstacles, which the laser drill could then drill past."

Water-filled crevasses would also pose a challenge. When one is drilled into, the laser drill would have to pump out water as it flows in before it could continue to drill deeper. However, drilling into these areas could help to identify the chemistry of potential habitats for past or present microbial life. If bacteria ever existed, their remains might be detectable in the samples collected from a laser-drilled borehole.

To make this type of laser drill possible, next steps would be miniaturizing the system, developing a dust-separation unit and completing space-qualification tests. A compact payload version could one day ride aboard a lander to an icy moon, bringing scientists closer to decoding the secrets frozen beneath alien surfaces, Koßagk said.

Meanwhile, back on Earth, the same tool could even help predict avalanches. Field tests in cooperation with the Austrian Research Centre for Forests and Department of Natural Hazards in the Alps and the Arctic showed that the laser drill can measure snow density without digging a pit — and, mounted on a drone, it could collect data from dangerous slopes where humans can't safely go, Koßagk said.

Whether on Earth or in deep space, the goal is the same: to look beneath the surface and understand what's hidden in the ice.

The team's initial findings were published Sept. 8 in the journal Acta Astronautica.

Young stars can be much more tumultuous than older stars. Stellar physics predicts that in our sun's formative years it was throwing off flares of radiation and coronal mass ejections (CMEs) far more powerful and more frequent than what the sun can manage today.

Yet no one had actually seen a young sun-like star being so energetic — until now.

A coronal mass ejection and its accompanying flare occur when taut magnetic field lines on the sun or another star snap, releasing a huge burst of energy before the field lines reconnect. This energy manifests as a brightening on the surface of the sun or star, while it can lift a huge plume of plasma straight from the corona, which is the ultra-hot outer layer of a star's atmosphere.

We're familiar with observing CMEs on our sun, but extraterrestrial CMEs are more difficult to spot. Nevertheless, ground-based telescopes observing at the hydrogen-alpha wavelength have detected cool, lower-energy plasma being burped off young stars during CMEs. The next step was to search for the higher-energy release of energy that stellar physicists believe characterizes the frequent CMEs from young stars.

To that end, a multi-national team of astronomers led by Kosuke Namekata of Kyoto University in Japan have made a breakthrough by targeting the young sun-like star EK Draconis, which is 112 light-years away from Earth in the constellation of Draco, the Dragon. The star is thought to be 50 million to 125 million years old, which is considered very young for a star that will exist for billions of years, and has a mass (0.95 solar masses), radius (0.94 solar radii) and surface temperature (5,560 to 5,700 kelvin) that are very close to the values for our sun.

"What inspired us most was the long-standing mystery of how the young sun's violent activity influenced the nascent Earth," said Namekata in a statement. "By combining space- and ground-based facilities across Japan, Korea and the United States, we were able to reconstruct what may have happened billions of years ago in our own solar system."

Namekata's team performed simultaneous observations of EK Draconis with the Hubble Space Telescope, NASA's Transiting Exoplanet Survey Satellite (TESS) and three ground-based telescopes in Japan and Korea. The Hubble observations were in ultraviolet light, which enabled the detection of the higher-energy components of a CME, while the ground-based telescopes tracked the cooler plasma via its hydrogen-alpha emission and TESS watched for brightening caused by the accompanying flare.

Together, Hubble and the ground-based telescopes detected the spectral lines from the emission of a CME on EK Draconis. Hubble's ultraviolet vision detected a cloud of hot plasma with a temperature of 100,000 kelvin (180,000 degrees Fahrenheit). The amount of Doppler shifting in the ultraviolet spectral lines from the star indicated that the hot plasma had been ejected at a velocity of 300 to 550 kilometers per second (670,000 to 1.2 million mph). Ten minutes later, a plume of cooler gas at 10,000 kelvin (18,000 degrees Fahrenheit) appeared, moving more slowly at 70 kilometers per second (157,000 mph). Together, the hot and fast component and cool and slow component were both two sides of the same CME.

The hot component of the CME carried much more energy than the cooler plasma. This much energy released on a regular basis, researchers said, would be significant enough to drive chemical reactions in a planetary atmosphere, producing greenhouse gases that could keep a planet warm, as well as breaking atmospheric molecules apart so they can reform as complex organic molecules that could potentially act as the building blocks of life. (No exoplanets have been detected orbiting EK Draconis yet, but it does have a probable red dwarf companion star.)

The observations therefore are a rare insight into the role that stars can play in the origin of life, a role that our sun may have played 4.5 billion years ago and which other stars may be doing today.

The findings were published on Oct. 27 in the journal Nature Astronomy.

For the past few years, astronomers including Beatriz Villarroel, of Nordita, Stockholm University, have been scrutinizing photographic plates exposed in the years before the Space Age began, as part of the Vanishing and Appearing Sources during a Century of Observations (VASCO) project. The aim of VASCO is to use archival data, now digitized, to search for new astrophysical transients, which are objects that brighten or fade, sometimes dramatically. These objects can appear as a spot of light in one image of the sky or space, only to vanish in the next.

Villarroel and study co-author Stephen Bruehl, a professor of anesthesiology from the Vanderbilt University School of Medicine, say their data show a statistical correlation between these flashes of light and reported sightings of unidentified objects. “We speculate that some transients could potentially be UAP in Earth orbit that, if descending into the atmosphere, might provide the stimulus for some UAP sightings,” they write in one of the new studies.

When VASCO launched, it had the stated aim of looking for stars that had vanished, which could for example signal a massive star collapsing into black hole without exploding as a supernova. VASCO could potentially also reveal new types of variable stars, active galactic nuclei, stellar flares or even brand new phenomena.

Sometimes the transients VASCO studies are unexplained, which has previously led Villarroel to a startling conclusion: that some of the objects detected on the plates are metallic objects in high Earth-orbit, before the launch of Sputnik 1 in 1957.

“Today we know that short flashes of light are often solar reflections from flat, highly reflective objects in orbit around the Earth, such as satellites and space debris, but the photographic plates analyzed in VASCO were taken before humans had satellites in space,” Villarroel said in a statement.

VASCO researchers analyzed 106,000 transients that look like stars that appeared and swiftly disappeared in a single exposure between the years 1951 and 1957. In particular, the appearance of the unidentified transients were 68% more likely to occur the day after a nuclear weapons test in Earth’s atmosphere than on other day, Bruehl added in the statement.

“The magnitude of the association between these flashes of light and nuclear tests was surprising, as was the very specific time at which they most often occurred – namely, the day after a test,” said Bruehl. “What they might represent is a very fascinating question that needs further investigation.”

In their study, Villarroel and Bruehl also found that the transients captured by the photographic plates increased by an average of 8.5% for each UAP sighting that was reported.

In a second study, which also included researchers from Algeria, India, Nigeria, Spain, Switzerland, Ukraine and the United States, they found that one anomalous transient coincided with a cluster of flying saucer sightings over Washington, D.C., on 27 July 1952. This particular transient, along with several others, was an instance where multiple flashes of light were seen along a narrow band. This, says Villarroel, suggests flat, reflective objects in motion high above Earth that were reflecting sunlight – a hypothesis supported by the fact that the number of mystery transients drops off in parts of the sky in Earth’s shadow, where sunlight can’t reach.

“You don’t get those kinds of solar reflections from round objects like asteroids or dust grains in space, which leave streaks during a 50-minute exposure, but only if something is very flat and very reflective and reflects the sunlight with a short flash,” said Villarroel.

Villarroel and Bruehl propose another possible explanation, however: that nuclear weapons tests triggered some unknown atmospheric phenomenon that went unnoticed at the time. But Villarroel and Bruehl are skeptical that such a phenomenon would stand still in the atmosphere for 24 hours between the weapons test and when the plate was exposed at Palomar in California. The transients do not seem to be particles of nuclear fallout that have drifted down onto the photographic plate either, since such particles would produce foggy, diffuse spots, not pinpoint, star-like objects.

The explanation Villarroel and Bruehl focus on most in their papers is that these transients are UAP of some kind. Their study connects the nuclear tests to sightings, which have been reported in the vicinity of nuclear sites for decades. "Significantly more UAP sightings were reported within nuclear weapons testing windows (test date + /- 1 day) than outside of testing windows," they report in their study.

There are, of course, many caveats. Critics have claimed that the transients could be photographic defects, or contamination, especially as the plates are quite old and were stored away for many decades before being digitized.

Villarroel and Bruehl perhaps also give too much credit to reports of UFO sightings. Their reported correlation of 8.5% between the appearance of the transients and flying saucer sightings is only relevant if it can be assumed those UAP sightings are credible in the first place. There may also be an observation bias – the 1950s were the heyday of UFO sightings, so it is perhaps not too surprising that there were sightings coinciding with the appearance of transients, since UAP sightings were reported on many different days.

Ultimately, correlation does not necessarily mean causation, and Villarroel and Bruehl do acknowledge this in their study.

In SETI, the search for extraterrestrial intelligence, researchers tend to assume that any unexplained phenomena isn’t aliens, and to exhaust every possible natural explanation before invoking an extraterrestrial one. This approach would be helpful here, although what those alternative explanations might be are not yet certain.

Because of the nuclear test-ban treaty there is, quite rightly, no way to test the hypothesis that the transients are related to atmospheric phenomena caused by nuclear explosions, of which there were at least 124 above the ground between 1951 and 1957.

For now, the discovery of the transients remains an intriguing puzzle. One possible way forward that has been suggested is to try and repeat the observations on the modern day sky. If geosynchronous satellites that we know about produce similar patterns of transients on photographic plates, then that would strengthen the hypothesis that the transients on the Palomar plates could depict metallic objects reflecting sunlight in high orbit.

The two studies are published in Scientific Reports and Publications of the Astronomical Society of the Pacific.

Over centuries, this curiosity evolved into a scientific pursuit, blending astronomy, biology, chemistry, and philosophy into a single, thrilling endeavor: to find life elsewhere in the cosmos.

From Galileo's telescope to the James Webb Space Telescope, each technological leap has brought us closer to answering that age-old question. We've sent probes to Mars, listened for alien signals through SETI, and discovered thousands of exoplanets orbiting distant stars. Along the way, we've refined our understanding of what life is, how it might arise, and where it could thrive — even in the most extreme environments.

This quiz explores the milestones, theories, and missions that have defined the search for extraterrestrial life.

Whether you're a space science enthusiast or just curious about the universe's biggest mystery, this challenge will stretch your mind across time and space.

Try it out below and see how well you score!

New laboratory research suggests that some organic molecules previously detected in plumes erupting from Saturn’s moon Enceladus may be products of natural radiation, rather than originating from the moon’s subsurface ocean. This discovery complicates the assessment of the astrobiological relevance of these compounds.

Enceladus hides a global ocean buried beneath its frozen crust. Material from this liquid reservoir is ejected into space from cracks in the ice near the south pole, forming plumes of dust-sized ice particles that extend for hundreds of kilometers. While most of this material falls back onto the surface, some remains in orbit, becoming part of Saturn’s E ring, the planet’s outermost and widest ring.

Between 2005 and 2015, NASA's Cassini spacecraft flew repeatedly through these plumes and detected a variety of organic molecules. The detection was viewed as evidence of a chemically rich and potentially habitable environment under the ice, where molecules essential to life could be available. However, the new study offers an explanation in which radiation, not biology, is behind the presence of at least some of these organic molecules.

To test the role of space radiation, a team of researchers led by planetary scientist Grace Richards, a postdoc at the National Institute for Astrophysics in Rome, simulated conditions near Enceladus's surface by creating a mixture of water, carbon dioxide, methane, and ammonia, the main expected components of surface ice on Enceladus. They cooled the concoction to −200°C inside a vacuum chamber and then bombarded it with water ions, which are an important component of the radiation environment that surrounds the moon.

The radiation induced a series of chemical reactions that produced a cocktail of molecules, including carbon monoxide, cyanate, ammonium, and various alcohols, as well as molecular precursors to amino acids such as formamide, acetylene, and acetaldehyde. The presence of these simple molecules indicates that radiation could induce similar reactions on Enceladus.

Richards presented these findings at the Europlanet Science Congress–Division for Planetary Sciences Joint Meeting (EPSC-DPS 2025) in Helsinki, Finland. She and her coauthors also published a detailed report in Planetary and Space Science.

Enceladus and beyond

The new research raises the question of whether the organic molecules detected in Enceladus's plumes truly come from the moon's buried ocean, whether they are formed in space, or whether they form close to the surface after the plumes leave the Enceladean interior.

While the finding doesn't exclude the possibility of a habitable ocean on Enceladus, Richards urges caution in assuming a direct link between the presence of these molecules in the plumes, their origin, and their possible role as precursors to biochemistry.

"I don’t necessarily think that my experiments discredit anything to do with Enceladus's habitability," Richards said.

However, she added, "when you're trying to infer this ocean composition from what you’re seeing in space, it's important to understand all the processes that go into modifying this material." Apart from radiation, these processes include phase changes, interactions with the moon's ice walls, and interactions with the space environment.

"We need a lot of experiments of that type," said planetary scientist Alexis Bouquet, a French National Centre for Scientific Research (CNRS) researcher at L'Université d’Aix-Marseille who wasn't involved in the study. "They demonstrated that you can produce a certain variety of species in conditions that are relevant to the south pole of Enceladus."

Bouquet highlighted the importance of simulating these environments in a lab for planning future missions to Enceladus and for interpreting the much-anticipated data from current missions to Jupiter's icy moons. These missions are NASA's Europa Clipper, which will explore Europa, and the European Space Agency's (ESA) JUICE (Jupiter Icy Moons Explorer), which will visit all three of the giant planet's moons with subsurface oceans: Ganymede, Calisto, and also Europa.

The intense radiation around Jupiter makes these experiments especially relevant. "Radiation chemistry for Europa or the Jovian moons in general [is] a big deal, a bigger deal than in Enceladus," Bouquet says.

Another Story Completely

As Richards's work questions the origin of organic compounds around Enceladus, researchers keep adding more molecules to the puzzle.

After a new analysis of data gathered during one of Cassini's close approaches to Enceladus in 2008, researchers led by planetary scientist Nozair Khawaja at the Freie Universität Berlin and the University of Stuttgart reported the discovery of new types of organic molecules, seemingly emanating from the icy vents. They include ester and ether groups and chains and cyclic species containing double bonds of oxygen and nitrogen.

On Earth, these molecules are essential links in a series of chemical reactions that ultimately produce complex compounds needed for life. And while these molecules could have an inorganic origin, "they increase the habitability potential of Enceladus,"
Khawaja said. The findings appeared in Nature Astronomy.

Khawaja's team's analysis suggests that complex organic molecules are present in fresh ice grains just expelled from the vents. During its last flyby, Cassini got as close as 28 kilometers to the moon's surface.

After modeling the plumes and the icy grains' residence times in space, they think that the ice grains sampled by Cassini did not spend a lot of time in space, likely just "a few minutes," Khawaja said. "It is fresh."

This short duration in space questions whether space radiation had enough time to produce the organic molecules Khawaja detected. Just a few minutes would not be long enough for such complex chemistry to take place, even in a high-radiation environment.

"Big grains coming from the surface full of organics? That is much harder to explain through radiation chemistry," Bouquet said.

While the types of experiments performed by Richards "are valuable and take the science to the next level," Khawaja said, "our results tell the other story completely."

Back to Enceladus

Both studies reinforce the complexity of Enceladus's chemistry, upholding it as a prime target in the search for extraterrestrial life, or at least life's building blocks. Enceladus has all three prerequisites for life: liquid water, an energy source, and a rich cocktail of chemical elements and molecules. Even if the subsurface ocean is out of reach—it lies at least a few kilometers beneath the ice close to the poles—the plumes offer the only known opportunity to sample an extraterrestrial liquid ocean.

Studies for a potential ESA mission dedicated to Enceladus are already underway, with plans that include high-speed flybys through the plumes and, potentially, a lander on the south pole. The insights from both recent studies will help researchers design the instrumentation and guide the interpretation of future results.

"There is no better place to look for [life] than Enceladus," Khawaja said.

The planet, known as GJ 251c, orbits a red dwarf star 18.2 light-years away in the constellation of Gemini, the Twins. The planet's mass is four times greater than that of Earth, making it a 'super-Earth' — a rocky planet larger and more massive than our own.

"While we can't yet confirm the presence of an atmosphere or life on GJ 251c, the planet represents a promising target for future exploration," said Suvrath Mahadevan, who is a professor of astronomy at Penn State University, said in a statement.

In the habitable zone, sometimes referred to as the Goldilocks zone, conditions are just right for liquid water to exist on the surface of a planet with an appropriate atmosphere.

GJ 251c was discovered thanks to observations spanning over 20 years, during which scientists looked for a slight wobble of the world's parent star incurred by the planet's gravity. As the star wobbles ever so slightly toward and away from us, we see a Doppler shift in its radial velocity that can be measured with a spectrograph.

One other planet is known to exist in the system, GJ 251b, which was discovered in 2020 and orbits its star every 14 days at a distance of 7.6 million miles (12.2 million kilometers). Using archive data from telescopes worldwide, a team of astronomers, including Mahadevan, was able to refine the accuracy of the radial velocity measurements for planet GJ 251b

The team then combined this refined data with brand new, high-precision observations from the Habitable-Zone Planet Finder (HPF), which is a near-infrared spectrograph on the Hobby-Eberly Telescope at McDonald Observatory in Texas. This revealed a second planetary signal belonging to a four-Earth-mass world orbiting the star every 54 days. That was then confirmed by measurements with the NEID spectrograph on the 3.5-meter WIYN telescope at Kitt Peak National Observatory in Arizona.

Though it may sound straightforward, in reality, the challenge of detecting the planet was formidable.

Stars are constantly roiling and churning as convective bubbles burst through to their visible surfaces and prominences splutter into space. This creates a noisy background of what's called asteroseismic activity that manifests as Doppler shifted lines in the star's spectrum. Picking out the Doppler shifted radial velocity signals from this noise is tricky, requiring a great deal of modeling what a planetary signal should look like.

"This is a hard game in terms of trying to beat down stellar activity as well as measuring its subtle signals, teasing out slight signals from what is essentially this frothing, magnetospheric cauldron of a star-surface," said Mahadevan.

Now that we know about the planet, astronomers can plan future observations.

GJ 251c is probably a little bit too far away from its star for the James Webb Space Telescope (JWST) to search for signs of an atmosphere around it. The next generation of 30-meter-class telescopes might be able to detect the planet's atmosphere via a method of searching for light reflected off its surface or atmosphere, but it will likely require the Habitable Worlds Observatory, which is a planned giant space telescope that is hoped to launch in the 2040s, to fully characterize GJ 251c.

"We are at the cutting edge of technology and analysis with this system," said Corey Beard of the University of California, Irvine, who participated in the research. "We need the next generation of telescopes to directly image this candidate."

Although GJ 251c is described by Mahadevan as being "one of the best candidates in the search for an atmospheric signature of life," referencing how we will search for biosignatures in the planet's atmosphere, there remains an elephant in the room: its star.

At 36% of the mass of our sun, the star GJ 251 is a red dwarf. Astronomers have now found numerous rocky planets in the habitable zone of red dwarfs, including Proxima Centauri b, TRAPPIST-1e and f, and Teegarden's Star b. However, red dwarfs are notorious for having violent tempers that bely their diminutive stature, releasing regular powerful flares that can over time strip a planet of its atmosphere. For example, the JWST's observations of the inner three planets of TRAPPIST-1 find no evidence for an atmosphere, while its observations of the fourth planet, e, are so far inconclusive. Some astronomers are now growing skeptical that Earth-like worlds can thrive around red dwarfs.

What GJ 251c has going for it is that it is slightly farther away from its star than habitable zone planets found around other red dwarfs are. This is thanks to its star being a little more massive than those other stars and therefore hotter, pushing the habitable zone farther out. It is possible that GJ 251c is far enough away from its star to have avoided the worst of its temper tantrums, and, if armed with a thick atmosphere and strong planetary magnetic field, it could have resisted the star's stellar wind from stripping its atmosphere away.

However, at present, this remains guesswork. "We made an exciting discovery," said Mahadevan, "But there’s still much more to learn about this planet."

The findings were reported on Oct. 23 in The Astronomical Journal.

A new study from NASA and Penn State University suggests fragments of biomolecules from ancient microbes could survive in Martian ice for tens of millions of years — long enough for future missions to potentially find them, according to a statement from the university.

In laboratory experiments simulating Mars conditions, researchers froze samples of E. coli bacteria in two different environments: pure water ice and a mixture of water and ingredients found in Martian soil, including silicate-based rocks and clay. The samples were cooled to minus 60 degrees Fahrenheit (minus 51.1 degrees Celsius) — the temperature of icy regions on Mars — and then exposed to radiation levels equivalent to what they would experience over 20 million years on Mars. The results were extended through modeling to represent 50 million years of exposure, according to the statement.

"Fifty million years is far greater than the expected age for some current surface ice deposits on Mars, which are often less than two million years old, meaning any organic life present within the ice would be preserved," Christopher House, co-author of the study and professor of geosciences, said in the statement. "That means if there are bacteria near the surface of Mars, future missions can find it."

The researchers found that the amino acids — the building blocks of proteins — survived far better in pure ice than in ice mixed with sediment. More than 10% of the original amino acids remained intact after the simulated 50-million-year exposure, while those in the soil mixture degraded 10 times faster and did not survive. When tested under even colder temperatures similar to those on Europa, an icy moon of Jupiter, and Enceladus, an icy moon of Saturn, the researchers found it further reduced the rate of deterioration.

Therefore, the researchers suggest that in pure ice, radiation byproducts such as free radicals become trapped and immobilized, slowing the chemical breakdown of biological molecules. In contrast, the minerals in Martian soil appear to create thin films of liquid that allow destructive particles to move and cause more damage.

"These results suggest that pure ice or ice-dominated regions are an ideal place to look for recent biological material on Mars," Alexander Pavlov, lead author and a space scientist at NASA Goddard Space Flight Center, said in the statement.

This can help better plan which areas to target during future Mars missions and how to design tools capable of drilling into subsurface ice deposits — most of which are believed to be less than two million years old, meaning any biomolecular traces from a more recent habitable period could be preserved in the frozen ice.

Their findings were published Sept. 12 in the journal Astrobiology.

This new detection on a brown dwarf is predicted by models that simulate alien atmospheres and is a reminder that phosphine is not necessarily a biosignature. However, astronomers remain puzzled about why some objects contain phosphine and others do not, even though theory says it should be there.

The phosphine was identified in the cold atmosphere of a brown dwarf called Wolf 1130C, which exists in a triple system along with a low-mass red dwarf star and a white dwarf. The phosphine exists with an abundance of 0.1 parts per million, which matches what models of the atmosphere of gas giant planets and brown dwarfs predict. Indeed, both Jupiter and Saturn contain a similar abundance of phosphine to Wolf 1130C.

The problem has been that many brown dwarfs that are expected to show detectable abundances of phosphine do not, and scientists don't know why.

Phosphine is a phosphorus-based molecule, composed of one atom of phosphorus and three hydrogen atoms. It is also pretty unstable in atmospheric conditions, and chemical reactions can easily break phosphine molecules apart. We see phosphine in Jupiter and Saturn's clouds because it is formed deep within the hot interiors of the giant planets, and then convection currents carry the phosphine to higher altitudes faster than the rate at which it is destroyed.

This is one of the reasons why the claimed detection of phosphine on Venus is so controversial.

It was in 2020 that a team led by Jane Greaves of the University of Cardiff in Wales detected phosphine in Venus' atmosphere using the James Clerk Maxwell Telescope in Hawaii and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. On Earth, phosphine occurs naturally as a product of biological processes, and Greaves' team strongly pushed the biological angle to explain their discovery, leading to speculation that there could be microbes living in Venus' toxic clouds.

However, a large section of the astronomical community differed with the team's findings, arguing that there were flaws in the analysis, and other groups have struggled to replicate the findings. In spite of this, Greaves' team has doubled down on their conclusions, and the presence of phosphine on Venus remains fiercely debated and controversial.

Part of scientists' disagreement with the discovery is that they find it hard to see how the phosphine could survive in Venus' atmosphere.

Nevertheless, phosphine is still considered a potential biosignature by astrobiologists in their search for alien life.

However, its existence in the clouds of Jupiter and Saturn, and now on Wolf 1130C, is a reminder that non-biological chemical processes can also produce phosphine. The question is why Jupiter, Saturn and Wolf 1130C have detectable levels of phosphine while other brown dwarfs that have been studied by JWST do not, or at least are so depleted in it that the molecule is not detectable.

There are several possible explanations. One is unique to the Wolf 1130 system. Before it evolved into a white dwarf, Wolf 1130B was a large star with a mass between six and eight times that of our sun. Such stars aren't quite massive enough to go supernova, so they end their lives much in the same way as our sun will — by expanding to become a red giant and then puffing off their outer layers to form a planetary nebula, while leaving behind their inert core as a white dwarf the size of Earth which, in the case of Wolf 1130B, packs in 1.24 solar masses.

Stars in the six-to-eight solar mass range can produce significant amounts of phosphorus in the latter stages of their life, which they can then belch out into space as the red giant shrugs off its outer layers. If this phosphorus-rich material was spewed all over Wolf 1130C, then it would explain where the phosphorus to form phosphine came from.

It's a nice theory, but unfortunately it doesn't pass muster. The white dwarf in the Wolf 1130 system forms a close binary with the low-mass star, Wolf 1130A, while the brown dwarf orbits the pair of them from a distance. A and B are so close that they are tidally locked to each other, meaning they show each other the same face constantly. Their relationship is even more involved than that — the gravitational pull of the white dwarf is actually stretching Wolf 1130A into an egg shape toward it.

When the star that formed the white dwarf died, the outer layers of the red giant would have engulfed Wolf 1130A. If the death of the star that became the white dwarf had deposited phosphorus onto the brown dwarf, then we'd also expect to see an over-abundance of phosphorus on Wolf 1130A, but we do not.

Another possibility is that the presence of phosphine is somehow related to the intrinsic chemical composition of the brown dwarf. Some models predict that atmospheres that contain very few elements heavier than helium have a preponderance for more phosphine. Indeed, 1130C does appear to have a very low abundance of these heavier elements, which astronomers refer to collectively as "metals." Similarly, Jupiter and Saturn also have low "metallicities."

The exact reason why a lack of heavy elements promotes phosphine is multifaceted: Not only does it help create the conditions in which phosphine can form and survive longer than it normally would, but the relative lack of other molecules present in the atmosphere means that there is less to interfere with the phosphine signal in the brown dwarf's spectrum, causing it to stand out more.

The problem is that other brown dwarfs observed by JWST also have low metallicities, but they don't show the expected amounts of phosphine.

These ambiguities prompt the authors of the new research, led by Adam Burgasser of the University of California, San Diego, to question how useful a biosignature phosphine is when we cannot even say for sure how it forms on distant planets and brown dwarfs.

"The inability of models to consistently explain all these sources indicates an incomplete understanding of phosphorus chemistry in low-temperature atmospheres," the authors said. "We therefore caution against the use of phosphine as a biosignature until these discrepancies are resolved."

If nothing else, the new study reminds us that, even if the detection of phosphine on Venus turns out to be real, its origin could very well be abiotic rather than biologically related. It's not time to get excited about life on any of these worlds just yet.

The findings were published on Oct. 2 in the journal Science.

On the western edge of Jezero Crater, NASA's Perseverance rover has been exploring Neretva Vallis, a river-carved valley that once fed a vast Martian lake. There, in an outcrop of ancient mudstone called the Bright Angel formation, the rover found one of its most intriguing targets yet: an arrowhead-shaped rock nicknamed Cheyava Falls, flecked with tiny black "poppy seeds" and ringed "leopard spots."

Closer analysis revealed that the strange markings are rich in organic carbon, iron, phosphorus and sulfur. More strikingly, scientists recently reported signs of vivianite (an iron phosphate) and greigite (an iron sulfide). On Earth, both minerals typically form through redox reactions — the electron-swapping processes that underpin all life. Plants rely on redox in photosynthesis, humans and other animals use it to extract energy from food during respiration, and microbes employ it to "breathe" metals in oxygen-starved settings such as deep-sea vents.

On our planet, such signatures are often the fingerprints of biology. On Mars, they remain a tantalizing "maybe" — chemical traces that could point to life, or could also arise from purely non-living processes. Either way, they mark a departure from the chemistry that scientists are used to seeing on the Red Planet.

"Whatever their origin, this is a very distinct chemistry than anything we've seen in ~20-25 years of roving the planet," Joel Hurowitz, a geoscientist at Stony Brook University in New York who led the recent study, told Space.com.

Even if the reactions turn out to be non-biological, he added, they could reveal "prebiotically useful chemistry we haven't thought about before," while also serving as a reminder of the ways that abiotic nature can mimic life's signals — false positives for biosignatures "that we'll have to do some really hard thinking about."

A window into Mars' past

Mars' surface usually tells a story of oxidation: iron reacting with oxygen billions of years ago, when liquid water and a thicker atmosphere were still present, leaving behind the global blanket of rust that earned Mars its enduring nickname, the Red Planet. At Cheyava Falls, however, Perseverance identified minerals that formed through the other half of the equation, known as reduction, where iron and sulfur gained electrons instead of losing them.

Redox reactions are especially compelling because, left to themselves, they proceed only sluggishly at low temperatures. That slow pace, and the energy locked within it, makes them an excellent fuel source for life. Life fast-forwards these reactions with enzymes, enabling microbes to seize the energy that would otherwise dissipate.

"All living things need to get energy from their environment. Life on Earth figured out how to do that very early by taking advantage of redox reactions," study co-author Mike Tice, a geobiologist at Texas A&M University in College Station, told Space.com.

Seeing evidence of redox chemistry on Mars, then, raises the possibility that similar processes could once have supported any life that may have emerged there.

"Based on what we know of life on Earth as well as some other theoretical factors, we think that life almost anywhere will probably wind up using redox reactions to get energy," said Tice. Searching ancient rocks for the chemical fingerprints of redox reactions, particularly cases where they appear to have unfolded faster than non-biological chemistry alone could explain, "is a key strategy for finding past life," he added.

That's what makes the minerals Perseverance spotted — particularly greigite in the leopard spots — so compelling. Abiotic sulfide production at low temperatures is extremely sluggish, according to Tice.

"They basically don't happen at the temperatures that we think these rocks experienced," he said. "So, the very things that make this particular redox reaction useful to some living organisms are the things that make it useful as potential evidence for life."

With rocks more than 3.5 billion years old, non-biological processes have had plenty of time to leave behind features that mimic biosignatures. At Cheyava Falls, though, the rocks show no signs of being altered by heat or pressure that could have driven fast chemical reactions, yet sulfides are present in notable amounts. For scientists, that discrepancy keeps open — but does not confirm — the possibility of a biological origin.

"It's very indirect evidence for life," Chris Impey, an astronomer at the University of Arizona who was not involved in the study, told Space.com. "It's not going to convince anyone that there's life on Mars beyond a reasonable doubt, which is at this point where the game is."

Gerard van Belle, the director of science at Lowell Observatory in Arizona, who was also not involved in the study, agreed. "It's not a smoking gun," he told Space.com. "The $100,000 question here is, Are those things something that would come from a uniquely biotic source, or are there abiotic ways?"

Still, these redox reactions intrigue scientists because they leave behind minerals that act like time capsules. Their chemistry and abundance preserve clues about the environment in which they formed — whether water once moved through the rocks, how oxygen-rich or oxygen-poor the environment was, and whether energy sources existed that microbes might have tapped.

The Bright Angel mudstone also looks chemically distinct from other Jezero rocks. It is unusually oxidized and stripped of elements like magnesium and calcium, a profile that Hurowitz said resembles soils on Earth that have been heavily weathered by long exposure to rain. That distinction likely reflects shifts in Mars' climate and atmosphere as Jezero Crater filled with sediment, the researcher said.

"The Bright Angel formation adds new dimensions to the overall picture of Mars' past environments," Hurowitz said. It tells scientists that the planet's climate and atmosphere may have varied considerably through time, "but also [have been] capable of supporting habitable environments while all of that variation was occurring."

Perseverance has already drilled a core from Cheyava Falls and cached it for eventual return to Earth. If all goes to plan with NASA's Mars Sample Return (MSR) mission campaign, scientists are eager to analyze the rock in ways impossible aboard the rover. (That's far from guaranteed, however; MSR has been plagued by delays and cost overruns, and President Donald Trump's 2026 proposed federal budget would cancel the project.)

Hurotwiz said he would "want to go right to work" on isotopic measurements of the Cheyava Falls sample — comparing lighter and heavier versions of iron, sulfur and carbon in the rock, particularly between the original mudstone and the newer minerals, vivianite and greigite, that crystallized within it. Differences in isotopic compositions between these reactants and products, he noted, "can be diagnostic in determining whether or not biology was involved in the redox reactions that formed them."

Van Belle said that returning pristine samples to Earth would make "a big difference" in the search for fossil-like structures — the kind of evidence that has long fueled debates, such as those over the famous Mars meteorite Allan Hills 84001, but this time without the uncertainty of contamination.

Tice said that, if someone had asked him two years ago whether life ever existed on Mars, his answer would have been that scientists simply didn't know enough to have a meaningful discussion. Previous NASA missions had shown that the Red Planet's surface could have supported life billions of years ago but didn't offer evidence for or against its habitation during that time.

Now, Perseverance is beginning to change that.

"We now have the first hints," he said, "and we can have real arguments and plan new observations constrained by the reality of actual rocks and minerals — that excites me!"

He likened the moment to treasure hunting. "This is the moment where the metal detector has gone off and you've dug up something shiny," he said. "You still need to find out exactly what you've got — but you've got something to work with."

"It's arguably the best evidence that we have so far for microbial life on early Mars," Oleg Abramov of the Planetary Science Institute told Space.com.

A rover and a rock

When Perseverance, trundling through an ancient river delta in Jezero crater on Mars, came across a large sedimentary rock that mission scientists have nicknamed "Cheyava Falls," it found something highly unusual, or at least unusual for Mars: light spots on the red rock, each spot ringed by dark material. Because of the way these features appear, scientists have referred to them as "leopard spots," and indeed we see similar spots on rocks on Earth.

Here, they can form in one of two ways.

One way is when iron-rich rock is exposed to high temperatures and acidic conditions, but neither are evident in the area around Cheyava Falls.

The other way? Life.

The rock Perseverance found appears to be rich in hematite, a common iron oxide that forms in liquid water — which makes sense because the rover is exploring an old, dried-up river valley and delta. Chemical reactions involving the hematite can turn the rock from red to white and produce iron rich minerals, in this case an iron phosphate called vivianite and an iron sulfide called greigite.Both are associated with microbial life on Earth in that they are useful energy sources. There's also organic material present (organic in this sense means molecules with at least one carbon atom, but not necessarily part of something that was living), preserved in the clay sediments, although Perseverance’s instruments are unable to determine what kind of organic molecules they are.

To be clear, Cheyava Falls is not confirmation that there was life on Mars. "But," Abramov says, "it's intriguing, and definitely worth further study."

The controversial Mars meteorite

However, this is not the first time the question of life on Mars has come up.

"There have been some hints of biological activity on Mars reported previously," said Abramov.

Back in 1996, NASA scientists led by David McKay claimed they had found minerals associated with life and even possible microfossils in a meteorite named ALH84001. It was located in Antarctica in 1984, but came from Mars. The discovery caused quite a stir, and the hype only increased when the finding was announced by former U.S. president Bill Clinton.

It didn't take long for the excitement to falter, however. Other researchers took a look at the data and found that inorganic processes or terrestrial contamination could replicate all the evidence from the meteorite.

Abramov points out that this does not disprove the Mars life explanation, but rather just presents an alternative, albeit much more probable, explanation for the evidence.

"It hasn't been ruled that what was observed in ALH84001 was a consequence of Martian biology — it may very well be," he said. "But while at the time it seemed fairly compelling evidence, in retrospect it was probably hyped up more than it should have been."

Abramov feels the astrobiology and planetary science communities have learned some lessons from the Martian meteorite saga in terms of how these discoveries, which carry with them a degree of ambiguity, are presented.

"ALH84001 actually shares some similarities with this new finding in Jezero," he said. "Both cases involve organic material and minerals that are generally precipitated by life. But this new finding in Jezero is arguably stronger evidence, but it's not being hyped up the way that ALH84001 was."

Methane on Mars

Another intriguing biosignature that is less controversial but still unexplained is the anomalous plumes of methane gas on Mars, first found by astronomers using ground-based telescopes in 2003, followed by the European Space Agency's Mars Express orbiter in 2004, and most recently by NASA's Curiosity rover and Europe's Trace Gas Orbiter. Unlike the uncertainty regarding the contents of the ALH84001 meteorite, the methane is definitely there, but where is it coming from?

Methane is easily destroyed by solar ultraviolet light, so something must be replenishing it on Mars. The methane plumes are also highly localized. On Earth, methane is largely produced by life, but there are also geophysical sources of the gas too, such as reactions between water and rock, or "serpentinization, "which is a chemical reaction involving carbon dioxide, water and olivine, which is a common mineral on Mars.

"The plumes are intriguing but ambiguous," said Abramov. "The levels of methane in the Martian atmosphere do seem to fluctuate, but they are very small amounts at the parts per million level, and we're not sure what the source is. It could be biological activity in the subsurface or maybe a hydrothermal-type environment, but it could also be something abiological."

Biosignatures beyond Mars

Furthermore, researchers are not only looking for and finding biosignatures on Mars; there is evidence for them elsewhere, too.

In 2020, astronomers led by Jane Greaves of the University of Cardiff claimed to have detected the gas phosphine in the atmosphere of Venus. The second planet from the sun has a completely inhospitable surface, with temperatures reaching 863 degrees Fahrenheit (462 degrees Celsius) and a crushing pressure underneath an oppressively thick atmosphere. There is, however, a region in its atmosphere at an altitude of over 31 miles (50 kilometers), where the temperature and pressure are almost Earth-like. On our planet, phosphine is produced only by life. Could its detection on Venus mean there is life in its clouds, or is some inorganic chemistry, unknown on Earth, producing it?

The discovery is controversial, however, because many other scientists have argued against the analysis of the data by Greaves' team and have mostly failed to detect the specific gas in their own observations, although there are claims of detecting phosphine on Venus by two instruments now: the James Clerk Maxwell Telescope in Hawaii and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. The issue might not get cleared up until new missions go to Venus; unfortunately, NASA's planned Venus missions are possible casualties of budget cuts facing NASA in the next financial year — although a European mission, named EnVision, is still set for launch in 2031.

More recently, there is the claim for the detection of a biosignature gas, dimethyl sulfide, in the atmosphere of an exoplanet called K2-18b. Some models suggest that K2-18b is a hycean world — an ocean planet with a thick atmosphere of hydrogen — and the signature of dimethyl sulfide was detected by the James Webb Space Telescope. However, just as with phosphine on Venus, the claimed detection has been strongly disputed. It is right at the limits of the JWST's abilities to detect, so we might not get confirmation one way or another until a larger space telescope is launched.

We don't necessarily have to face that problem for Mars and Cheyava Falls. Perseverance has taken a sample of the rock, stowing it away in a protective canister for a future mission to pick up and return to Earth.

"It would be great to get those samples back to Earth and into a terrestrial laboratory," says Abramov. "Then we could analyze those samples to high resolution, and we might find other lines of evidence such as potential microfossils and other minerals."

However, those waiting for a eureka moment, a definite discovery, might still be in for disappointment. It's easy to forget that the biosignature on Cheyava Falls is billions of years old, and what we're seeing is a trace, of a trace, of a trace, of what might have been connected to microbial life in the past.

"In terms of a definitive answer, the way I look at it is, as scientists, we get closer and closer to the truth without quite getting there," says Abramov. "So in terms of saying definitively whether it is life or not, that is going to be very difficult if not impossible."

Unfortunately, NASA's planned Mars Sample Return mission to collect Perseverance's sample canisters is under threat. Technical and cost problems have seen NASA turn to private aerospace companies to see if they can come up with a solution to making the mission successful, but even if they can, it might not survive the cost-cutting facing NASA in the Trump Administration's planned budget for the 2026 financial year.

"Getting those samples to Earth and analyzing them in proper labs is going to be our best chance of understanding what's happening," says Abramov.

Only then could scientists make possibly the greatest discovery in history: the discovery of life, past or present, on another planet.

Enceladus is one of the most intriguing moons in the solar system due to the discovery by NASA's Cassini probe of plumes of water ice erupting from the moon's south polar region. The find indicates geological activity on Enceladus, along with a subsurface ocean of liquid water — and perhaps even an environment capable of sustaining life.

ESA is now targeting a mission to study enigmatic Enceladus as part of its Voyage 2050, the agency's long-term plan for space science activities, according to ESA officials at the Europlanet Science Congress (EPSC) and Division for Planetary Sciences (DPS) joint meeting, which was held in Helsinki in early September.

The Enceladus mission, though in its earliest stages, will need both an orbiter and a lander to answer major science questions, with the orbiter to be designed to sample material in the plumes emanating from the "tiger stripes" at the south pole.

An early mission configuration following first industrial studies calls for two launches of the largest variant of the Ariane 6 rocket, with spacecraft to dock in Earth orbit. Next, approval is needed at the ESA ministerial meeting in Bremen, Germany, in November, allowing a mission definition phase, leading to mission adoption in 2034 and a launch around 2042. The spacecraft would then arrive in the Saturn system in 2053, starting a tour of Enceladus and other moons, collection of plume material and preparation for a landing around 2058.

Jörn Helbert of ESA's European Space Research and Technology Centre (ESTEC) stated in a presentation at EPSC-DPS that, since March of this year, the ESA study team has been working with a newly selected payload working group and an expert committee to refine the science requirements and identify key technologies.

The Enceladus mission aims to advance European expertise in several scientific and technological fields, including in-orbit assembly, operating in extreme environments, landing technologies and novel scientific instrumentation, according to Helbert. He added that the development of these technologies will have wide-ranging applications beyond ESA's space science program.

Helbert noted that Enceladus has three necessary conditions for supporting life as we know it: the presence of liquid water, a source of energy and a specific set of chemical elements. An answer to the question of whether or not life exists below Enceladus's icy shell may, however, require decades of efforts in terms of planning, resources and innovation.

Planets lacking plate tectonics and sufficient carbon dioxide and oxygen could make advanced civilizations like ours extremely rare, Manuel Scherf and Helmut Lammer of the Austrian Academy of Sciences suggested during a presentation at the Europlanet Science Congress and the Division for Planetary Science (EPSC-DPS) in Helsinki earlier this month.

According to their research, for a biosphere to persist long enough to allow for the evolution of complex life and subsequent advanced technology, an Earth-like planet needs to meet certain criteria.

First, there must be enough carbon dioxide to sustain photosynthesis and prevent atmospheric escape — but not too much that the atmosphere becomes toxic or traps too much heat. The key to this balance is plate tectonics, which regulate the amount of atmospheric carbon dioxide via the carbon-silicate cycle.

But plate tectonics won't maintain the biosphere forever. "At some point, enough carbon dioxide will be drawn from the atmosphere so that photosynthesis will stop working. For the Earth, that's expected to happen in about 200 million to roughly one billion years," Scherf said in a statement. Thus, a planet would also need a life-sustaining biosphere that lasts longer than the time it takes for technologically intelligent life to evolve. On Earth, that evolution took 4.5 billion years.

Second, a world must have a nitrogen-oxygen dominant atmosphere to develop an advanced civilization. Oxygen, in particular, is crucial not only for biology but also for technological advancement. For example, levels below about 18% oxygen could prevent the use of fire, which historically has been essential for metalworking and thus the development of advanced tools.

The team created models to compare the lifespans of biospheres with various atmospheric compositions to the amount of time it might take advanced civilizations to evolve. They concluded that if an advanced technological civilization were to exist in our Milky Way galaxy, the closest it would be to Earth is likely about 33,000 light-years away. Such a civilization would also have to survive for at least 280,000 years — and possibly much longer — for there to be any chance it overlaps with ours in time.

In other words, the odds are very slim that we coexist with another intelligent civilization in the Milky Way.

Despite the grim outlook, the authors encourage continued efforts, especially through SETI (the search for extraterrestrial intelligence). "Although ETIs [extraterrestrial intelligences] might be rare, there is only one way to really find out, and that is by searching for it," said Scherf. "If these searches find nothing, it makes our theory more likely, and if SETI does find something, then it will be one of the biggest scientific breakthroughs ever achieved, as we would know that we are not alone in the universe."

For years, scientists thought these planets, which are larger than Earth but smaller than Neptune, could form far from their stars, sweeping up ice beyond the so-called "snow line." As the planets migrated inward, scientists have thought that ice might melt into oceans hidden beneath hydrogen skies. Such hypothetical worlds were dubbed "Hycean planets," a blend of "hydrogen" and "ocean."

"Our calculations show that this scenario is not possible," Caroline Dorn, an assistant professor of Physics at ETH Zürich in Switzerland who co-led the new study, said in a statement.

The results come just months after high-profile claims about K2-18b, an exoplanet about 124 light-years away, made global headlines as a likely ocean world "teeming with life." A team of scientists studying James Webb Space Telescope (JWST) observations had reported hints of a possible biomarker gas, dimethyl sulfide, on K2-18b — fueling speculation that the planet might be cloaked in a hydrogen-rich atmosphere above a vast global ocean. These are conditions that could potentially support life (as we know it).

But those claims were quickly met with pushback. Independent analyses of the same JWST data suggested the team's evidence for DMS was weak at best, while other experts cautioned that sub-Neptunes may not be ocean-bearing worlds at all, but rather volatile-rich planets wrapped in thick, hostile atmospheres.

In the new study, Dorn and her team modeled how sub-Neptunes evolve during their early lifetimes, when they are thought to be blanketed by hydrogen gas and covered for millions of years by molten rock. Unlike earlier studies, the researchers included chemical interactions between magma and the atmosphere, according to the statement.

Of the 248 model planets the team studied, "there are no distant worlds with massive layers of water where water makes up around 50 percent of the planet's mass, as was previously thought," Dorn said in the statement. "Hycean worlds with 10-90 percent water are therefore very unlikely."

The team found that hydrogen and oxygen — the building blocks of H2O — tend to bind with metals and silicates in the interior, effectively sequestering water deep in the interior. Even planets that began with abundant ice ended up with less than 1.5% of their mass as water near the surface, the new study reports, far less than the tens of percent envisioned for Hycean planets.

"We focus on the major trends and can clearly see in the simulations that the planets have much less water than they originally accumulated," Aaron Werlen, a researcher on Dorn's team at ETH Zürich who co-led the new study, said in the same statement. "The water that actually remains on the surface as H2O is limited to a few per cent at most."

The researchers also found that the most water-rich atmospheres did not appear on planets formed far from their stars, where ice is plentiful, but rather on planets formed closer in. In these cases, water was generated chemically, as hydrogen in the atmosphere reacted with oxygen from the molten rock.

The implications are sobering for astrobiology. If Hycean planets do not exist, the most promising havens for liquid water, and potentially life, may lie on smaller, rocky worlds more akin to Earth.

Still, K2-18b remains a captivating target, scientists say. As a sub-Neptune, a type of planet missing from our own solar system but common across the galaxy, it could reveal fundamental insights into how planetary systems form and why ours turned out the way it did.

The new results also suggest that Earth may not be exceptional, with many distant worlds veiled in similarly modest traces of water.

"The Earth may not be as extraordinary as we think," Dorn said in the statement. "In our study, at least, it appears to be a typical planet."

The research was published on Sept. 18 in The Astrophysical Journal Letters.

In the study, scientists identified 24 minerals that chart Jezero's changing environment, highlighting both the volcanic origins of rocks in the crater and a long history of their interaction with water. Although the research does not analyze the Sapphire Canyon sample directly, it shows the crater as a whole experienced multiple episodes of water activity, each with conditions that could have supported life (as we know it).

"There were several times in Mars' history when these particular volcanic rocks interacted with liquid water," study lead author Eleanor Moreland of Rice University in Texas said in a statement, "and therefore more than one time when this location hosted environments potentially suitable for life."

The study draws on three years of data collected by Perseverance, which has been exploring Jezero since landing on Mars in 2021. Using the rover's X-ray instrument (PIXL) and a newly developed algorithm called MIST, researchers were able to identify the minerals and assemble a so-called "mineralogical archive" of the crater, according to the statement.

Minerals are natural storytellers, forming under specific combinations of temperature, chemistry and pH. At Jezero, they reveal three stages of water-rock interaction, each with different implications for habitability, the new study notes. To ensure accuracy, the team ran their identifications through thousands of statistical simulations — a process likened to how meteorologists model hurricane tracks — to account for instrument error and assign confidence levels to each match, according to the statement.

The oldest rocks on the crater floor bore signs of hot, acidic fluids, recorded in minerals such as greenalite, hisingerite and ferroaluminoceladonite. These conditions would have been least favorable for life, scientists say, as high temperatures and low pH are known to damage biological structures.

"These hot, acidic conditions would be the most challenging for life," study co-author Kirsten Siebach, who is an assistant professor of Earth, environmental and planetary sciences at Rice University, said in the statement. "But on Earth, life can persist even in extreme environments like the acidic pools of water at Yellowstone, so it doesn't rule out habitability."

Later episodes of water activity left behind minerals such as minnesotaite and clinoptilolite, which formed in cooler, more neutral waters that would have been friendlier to microbes, the study reports.

Finally, researchers found widespread deposits of sepiolite, a mineral that forms in low-temperature, alkaline waters considered highly hospitable from an Earth perspective. Its presence across all regions Perseverance has explored suggests a broad episode of habitable conditions, scientists say.

"These minerals tell us that Jezero experienced a shift from harsher, hot, acidic fluids to more neutral and alkaline ones over time — conditions we think of as increasingly supportive of life," Moreland said in the statement.

Alongside these alteration minerals, the team also confirmed the presence of volcanic building blocks such as pyroxene, feldspar and olivine, reinforcing the prevailing view that Jezero's floor was formed by ancient lava flows later transformed by water.

The new findings also add context to last year's headlines, when Perseverance's work at Cheyava Falls — where Sapphire Canyon was sampled — revealed intriguing signs of conditions often linked to microbial life. At the time, scientists described it as the strongest evidence yet that Mars may once have hosted primitive organisms, though they stressed that nonbiological explanations, such as certain mineral reactions from heating, could not be ruled out.

Follow-up analyses have since found no evidence the rock was heated, but researchers caution that only laboratory studies on Earth can settle the biological-versus-nonbiological debate.

"We're pretty close to the limits of what the rover can do on the surface," Katie Stack Morgan, Perseverance Project Scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, said during a press conference last week on Sept. 10. "That was by design. The payload of the Perseverance rover was selected with a Mars sample return effort in mind; the idea was for our payload to get us just up to the potential biosignature designation and have the rest of the story told by instruments here on Earth."

Each tube cached on Mars could hold a crucial piece of the puzzle — and perhaps, the first direct evidence of life beyond Earth. But the path to bringing them home continues to remain uncertain. After years of cost overruns, NASA announced in January that it would study cheaper alternatives for its proposed Mars Sample Return (MSR) program, which would aim to deliver samples by 2035. The agency's 2026 budget proposal, however, calls for canceling the program.

"We believe there is a better way to do this, a faster way to get these samples back," Sean Duffy, NASA's acting administrator, said during the press conference last week, , though he offered no details on cost, timing, or technical approach.

Meanwhile, China is pushing ahead with its own Mars sample-return mission. The Tianwen-3 mission aims to collect at least 500 grams of Martian rock and soil as early as 2028 and return them to Earth by 2031 — potentially beating NASA to the milestone. If successful, China would secure the first Mars samples and perform a dramatic leap in planetary science leadership.

In addition to revealing Mars' mineral story, the new MIST algorithm developed by the study authors could prove critical in deciding which rocks to return to Earth, the new study notes. By identifying minerals and assigning confidence levels to each detection, it helps mission scientists prioritize the most valuable samples. Such a catalog, tied to specific sampling sites, would be vital when selecting which sealed cores to bring back under the MSR program.

"The results reported here can be crucial when down-selecting which samples, if not all, are returned to Earth," the researchers wrote in the study.

The study was published on Sept. 11 in the Journal of Geophysical Research.

The first planets studied by the ATREIDES program, the two worlds of the TOI-421 system, demonstrate misaligned orbits, hinting that this system experienced a more chaotic evolution than our solar system. Studying it could help astronomers figure out why these "hot Neptunes" appear to be so rare in the cosmos, as well as teach us about how planets form elsewhere in the universe.

"The complexity of the exo-Neptunian landscape provides a unique window onto the processes involved in the formation and evolution of planetary systems," ATREIDES Principal Investigator and University of Geneva (UNIGE) researcher Vincent Bourrier said in a statement describing the ATREIDES program.

To understand why this class of extrasolar planet, or "exoplanet," is missing from close orbits around other stars, ATREIDES scientists investigated the TOI-421 planetary system. Located around 244 light-years from Earth, TOI-421 is an orange dwarf or "K-type" star orbited by two exoplanets, TOI-421 b and TOI-421 c. What this investigation revealed is a surprisingly tilted orbital situation in TOI-421 that implies that this system experienced a chaotic history, one which may help explain why hot Neptunes are so rare.

TOI-421 b is a scorching hot sub-Neptune planet with a mass around 7 times that of Earth that orbits its star at a distance equivalent to around 6% of the distance between our planet and the sun. TOI-421 c is larger, with a mass of around 14 times that of Earth, which orbits its star at a distance equivalent to around 12% the distance between Earth and the sun, making it a hot Neptune and putting it in a region adjacent to the Neptunian desert called "the savanna."

"A thorough understanding of the mechanisms that shape the Neptunian desert, savanna, and ridge will provide a better understanding of planetary formation as a whole ... but it's a safe bet that the universe has other surprises in store for us, which will force us to develop new theories," Bourrier said.

Mapping the Neptunian desert

Over the last 10 years of exoplanet observations, the Neptunian desert has become increasingly complex. Areas further out from stars than the Neptunian desert have been found to be more generously populated with Neptune-sized worlds. This more temperate realm with more Neptune-like exoplanets has come to be known as the "savanna" of the Neptunian desert.

Astronomers have also defined a region between the Savanna and the Neptunian desert, which they call the "Neptunian ridge." This region is more densely populated by Neptune-like worlds than both the desert and the savanna. The scientists of the ATREIDES program aim to understand these three distinct regions by identifying the processes that lead to the relative planetary populations.

The team wants to test the hypothesis that the Neptunian landscape is created as a result of the way that planets migrate from their birthplaces to the orbits we observe them in.

Some exiled planets would migrate slowly through the disk of gas and dust that exists in these systems during their infancy. This sedate migration should produce planets in orbits aligned with their star's equator and the orbits of the other planets in their home system. That is similar to the orbits of the planets in the solar system, which are aligned almost to the equatorial plane of the sun.

However, some other planets would be violently thrown from their site of formation via a chaotic process called "high-eccentricity migration." That should result in those planets falling into highly misaligned orbits.

That means the alignment between a star's orbital plane and the orbital plane of its planets is key to investigating this migration hypothesis.

The team can't yet say anything conclusive yet about the Neptunian desert, its neighboring regions, or planetary evolution in general. Many more observations of more planetary systems with hot Neptunes will be needed for that.

However, this research successfully demonstrates the effectiveness of the ATREIDES program and the techniques it has developed and employed.

The team's research was published on Tuesday (Sept. 16) in the journal Astronomy & Astrophysics.

But new research presented this week at a planetary science conference in Finland shows that many of the organic molecules detected in these plumes could also form right on the moon's surface, driven by relentless radiation from Saturn's magnetic field. The results cast doubt on whether the plumes truly carry whispers of alien life, or merely echoes of lifeless chemistry on the frozen shell.

"Although this doesn't rule out the possibility that Enceladus' ocean may be habitable, it does mean we need to be cautious in making that assumption just because of the composition of the plumes," study lead Grace Richards of Italy's National Institute for Astrophysics said in a statement.

For their experiment, Richards and her colleagues recreated conditions on Enceladus in miniature inside a specialized laboratory in Hungary. Using an ice chamber, the team froze mixtures of water, carbon dioxide, methane and ammonia to a bone-chilling –420 degrees Fahrenheit (-253 degrees Celsius), mimicking frigid conditions near the moon's surface. The ices were then bombarded with high-energy "water-group ions," the same charged particles trapped around Saturn that constantly irradiate Enceladus.

To monitor the chemical changes induced by radiation, the researchers used infrared spectroscopy to observe the molecular "fingerprints," or spectra, of the ices. As radiation interacted with the samples, the spectra shifted, signaling the formation of new molecules.

Each of the five experiments produced carbon monoxide, cyanate, and ammonium — compounds that were detected in Enceladus' plumes by NASA's Cassini spacecraft in 2005. When the samples were gently warmed, more complex organics appeared, including carbamic acid, ammonium carbamate and potential amino acid precursors including methanol and ethanol, as well as molecules like acetylene, acetaldehyde and formamide, which are building blocks that could contribute to the chemistry of life.

"Although many of these products have not previously been detected on Enceladus' surface, some have been detected in Enceladus' plumes," Richards and her colleagues wrote in the paper. This leads to "questions about whether plume material is formed within the radiation-rich space environment or whether it originates in the subsurface ocean."

Crucially, the timescales necessary for radiation to drive these chemical reactions are comparable to how long ice remains exposed on Enceladus' surface or in its plumes, so distinguishing ocean-sourced organics from surface-born ones may be difficult, the study notes.

"It is likely that the composition of the subsurface ocean may not be accurately reflected by the composition of the emergent plume, or by material deposited on the surface immediately adjacent to the plume," the paper reads.

For astrobiologists, the results are both sobering and exciting. On one hand, they complicate the story that organics in the plumes are definitive signs of a life-friendly ocean. On the other, they highlight that rich, potentially life-relevant chemistry can thrive even in extreme, radiation-battered environments, thereby expanding the ways scientists think about where prebiotic molecules might form and why Enceladus remains a prime target for exploration.

NASA's Cassini mission, which ended in 2017 with a dramatic plunge into Saturn's atmosphere, gave humanity its first and only direct "taste" of Enceladus' geysers. But instruments onboard the spacecraft weren't designed to distinguish between molecules forged in the moon's presumably deep ocean and those cooked up in the icy shell.

These answers could come in the coming decades with future missions. One concept under consideration as part of the European Space Agency's Voyage 2050 program envisions a dedicated probe that could land on the surface and collect material ejected from the moon's hidden ocean. NASA has also previously studied an "Orbilander" concept designed to sample Enceladus' plumes from orbit.

Meanwhile, China is exploring a multi-part mission architecture that would include an orbiter, a lander and a deep-drilling robot that would attempt to reach the subsurface ocean to search for potential biosignatures.

This research is described in a paper published in the October 15 edition of the journal Planetary & Space Science.

Since February 2021, NASA's Perseverance rover has been exploring a region on Mars known as Jezero Crater, a huge cavity believed to have once hosted a lake. It's considered one of the most promising places to look for evidence of ancient life on the Red Planet (life as we know it, at least) — and there has been an update in the search.

On Wednesday (Sept. 10), researchers presented a study that describes how Perseverance found intriguing minerals on the western edge of Jezero Crater, in the clay-rich, mudstone rocks of a valley called "Neretva Vallis."

"When we see features like this in sediment on Earth, these minerals are often the byproduct of microbial metabolisms that are consuming organic matter," Joel Hurowitz, a planetary scientist at Stony Brook University in New York and lead author of the new study, said during a NASA press conference held on Wednesday.

So, could this mean we've finally found proof of aliens? Well, not quite. The authors stress that further analysis is necessary to identify the true origin of the minerals and determine whether they are indeed markers of life, otherwise known as "biosignatures," or the result of some other inorganic processes.

"I want to remind everyone that what we're describing here is a potential biosignature that is a characteristic element, molecule, substance or feature that might have a biological origin but requires more data or further study before reaching a conclusion about the presence or absence of life," Lindsay Hayes, Senior Scientist for Mars Exploration in the Planetary Science Division at NASA Headquarters, said during the conference.

Either way, the findings do demonstrate that notably complex reactions once occurred on Mars — organic or not — adding yet more layers to the planet humans have been trying to decode since the dawn of astronomy.

To get into some specifics, the samples Perseverance collected that appear to harbor those exciting minerals were found in what's known as the "Bright Angel" formation within the northern margin of Neretva Vallis. Within that formation, one particular rock is of great interest to researchers. It's named "Cheyava Falls."

Not too long ago, when Cheyava Falls was first presented to the public, it made headlines around the world because scientists were openly fawning over the specimen's peculiar, dotty features that resembled "poppy seeds" and "leopard spots." The latter, which are millimeter-size blobs, are each surrounded by black rings that scientists determined contain iron and phosphate after studying them with Perseverance's toolkit. Both substances can result from chemical processes on Earth that are driven by microbes.

"These spots are a big surprise," David Flannery, an astrobiologist and member of the Perseverance science team from the Queensland University of Technology in Australia, said at the time. "On Earth, these types of features in rocks are often associated with the fossilized record of microbes living in the subsurface."

"What we saw in this rock were these layers of very fine-grained, rusty red mud stone that had in them these incredible features," Hurowitz said. "These textural features told us that something really interesting had happened in these rocks, some set of chemical reactions occurred at the time they were being deposited."

The natural next step was to have Perseverance examine Cheyava Falls (and other specimens associated with Bright Angel) a little more closely. On July 21, 2024, the rover even drilled into Cheyava Falls and collected a sample. This sample, the 25th that Perseverance had grabbed, is named Sapphire Canyon.

"I would describe the Sapphire Canyon sample as mysterious," Morgan Cable, a research scientist for Perseverance, previously said in a video about the core sample that NASA posted on April 10. "We see these signatures that tell us chemistry has happened, potentially involving organics — but what does that mean? Could life have been involved, or something that didn't involve life at all?"

That's sort of where the tale left off.

Now, what the new study appears to add to the story is a very detailed analysis of the Bright Angel bunch. Sure enough, the researchers found evidence that this outcrop really could be a solid lead in the quest to find proof of life beyond Earth. According to a release about the results, the team "identified tiny nodules and specks enriched in iron phosphate and iron sulfide. These features are associated with organic carbon and appear to have formed after sediment deposition, under low-temperature conditions."

The key seems to be the result that certain "redox" reactions could have occurred to give rise to these minerals. A redox reaction is a chemical reaction in which electrons are transferred between two substances; one of the substances is oxidized and the other is reduced.

"This organic carbon appears to have participated in post-depositional redox reactions that produced the observed iron-phosphate and iron-sulfide minerals," the study authors wrote.

"The exciting discovery of reduced iron phosphates and sulfides associated with organic compounds in the clay-rich mudstones of Jezero Crater suggests that the organic material might have been involved in the unusual redox reactions," states a News and Views article, written by Janice Bishop of SETI Institute in Mountain View, California and Mario Parente of the University of Massachusetts, Amherst. This article was published in tandem with the study results.

"On Earth, microorganisms commonly interact with minerals and have been observed to convert sulfates (which contain oxidized sulfur atoms) to sulfides (which contain reduced sulfurs) in cold, oxygen-free Antarctic lakes," the News and Views article continues. "There is no evidence of microbes on Mars today, but if any had been present on ancient Mars, they too might have reduced sulfate minerals to form sulfides in such a lake at Jezero crater."

A few other results presented in the team's paper strengthen the case of a possible biosignature existing in Mars' Bright Angel formation as well. For instance, the new findings suggest the green-toned specks in muddy clay found in the outcrop could contain the mineral vivianite, which the News and Views authors say can specifically shed light on certain kinds of redox reactions that may have taken place on Mars.

All in all, however, there is one major underlying elephant in the room: For any further confirmation of whether evidence of Mars life lies in Perseverance's sample tubes, those sample tubes need to be returned to Earth. Unfortunately, as of now, NASA's Mars Sample Return program remains in limbo due to budget constraints, priority shifts since the Trump administration took the White House and a highly complicated blueprint for the mission.

Still, scientists continue to stress that there is only so much one can do when analyzing tiny rock samples while separated by a 140-million-mile (225-million-kilometer) stretch of the vacuum of space.

"We're pretty close to the limits of what the rover can do on the surface," Katie Stack Morgan, Perseverance Project Scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, said during the conference. "That was by design. The payload of the Perseverance rover was selected with a Mars sample return effort in mind; the idea was for our payload to get us just up to the potential biosignature designation and have the rest of the story told by instruments here on Earth."

"Laboratory analyses of samples returned from Mars could also cast light on the potential for prebiotic — and even biological — chemistry to occur on worlds beyond Earth," the News and Views authors write.

UFOs are coming back to Washington, D.C. tomorrow.

A hearing titled "Restoring Public Trust Through UAP Transparency and Whistleblower Protection" will be held by the Task Force on the Declassification of Federal Secrets, a task force established in January 2025 by the House Committee on Oversight and Government Reform. At the hearing, three U.S. military veterans will share their experiences witnessing UAP, or unidentified anomalous phenomena, a new term for UFOs that encompasses strange objects or events not only in the sky but also in water or space, or that appear to travel between these domains.

The hearing begins at 10 a.m. ET (1400 GMT) on Tuesday (Sept. 9). Watch it live here courtesy of the House Committee on Oversight and Reform.

The Task Force is chaired by Representative Anna Paulina Luna (R-Fla.), who has alleged that the U.S. government is hiding the truth about many other conspiracies. "It is time to give Americans the answers they deserve, which is why I am honored to lead this bipartisan task force that seeks truth and transparency," Luna said in a House statement announcing the task force. "We will also investigate UAPs/USOs, the Epstein client list, COVID-19 origins, and the 9/11 files."

Luna says tomorrow's hearing is intended to compel Congress to reexamine what types of information should be classified and which should be available to the public, mostly when it comes to UAP. "The American people deserve maximum transparency from the federal government on sightings, acquisitions, and examinations of UAPs and whether they pose a potential threat to Americans' safety," Luna said in a House statement announcing the hearing.

In addition to the three military veterans who claim to have witnessed UAP, the hearing will also include longtime investigative journalist George Knapp. For decades, Knapp has claimed the U.S. government is hiding evidence of UFOs and/or alien life. In the late 1980s while working as anchor for KLAS-TV in Las Vegas, Knapp rose to fame helping popularize the claims of UFO-lore stalwarts Bob Lazar and John Lear.

Lazar claims to have worked at the U.S. Air Force's infamous Area 51 facility where he helped reverse engineer crashed flying saucers. His claims have never been substantiated.

Lear, meanwhile, was a former CIA pilot who promoted theories that the U.S. government was involved in a long-term conspiracy to hide the fact that it colluded with extraterrestrial beings.

Ultimately, Tuesday's hearing is intended to send the message that "whistleblowers who provide details on spending information and policies and procedures regarding the classification and declassification of UAPs should be able to do so without retribution," according to Luna's statement.

We've heard similar sentiments in previous congressional hearings. In November 2024, former U.S. counterintelligence officer Luis Elizondo, who claims to have investigated UAP while working for secret Pentagon program, testified that we are "in the midst of a multi-decade, secretive arms race  — one funded by misallocated taxpayer dollars and hidden from our elected representatives and oversight bodies."

Elizondo, who has shared easily debunked imagery as proof of UAP in other congressional briefings, suggested the U.S. government should offer protections to UAP whistleblowers so those who are "desperate to do the right thing can come forward without fear."

For decades, purported whistleblowers have argued that classified military and intelligence sensors and satellites regularly record evidence of unexplained phenomena or advanced craft, potentially piloted by alien beings.

But because those records are classified by the U.S. government in order to not reveal the full extent of its surveillance or sensing capabilities, these whistleblowers argue, the truth is being withheld from the American public and the world.

The planet in question is TRAPPIST-1e, an Earth-sized rocky exoplanet that's located around 40 light-years away from our planet.

TRAPPIST-1e is the fourth planet in orbit around a red dwarf star called TRAPPIST-1. It sits well within the "habitable zone" or Goldilocks zone, the region of space around a star that is neither too hot nor too cold to allow liquid water to exist on the surface of a planet.

However, just existing in the habitable zone of a star isn't sufficient to guarantee the existence of liquid-water oceans or indeed the conditions needed to support life. After all, Earth, Mars, and Venus are all in our solar system's habitable zone, but only one of these planets has water oceans and supports life today (as far as we know). One of the key differences is the atmosphere of our planet, and that is what astronomers are searching for around TRAPPIST-1e.

"TRAPPIST-1e has long been considered one of the best habitable zone planets to search for an atmosphere," study team member Ryan MacDonald, a researcher at the University of St. Andrews in Scotland, said in a statement. "But when our observations came down in 2023, we quickly realized that the system’s red dwarf star was contaminating our data in ways that made the search for an atmosphere extremely challenging."

The JWST data indicate several possible scenarios for TRAPPIST-1e and its potential atmosphere. That makes this research a significant step forward in the search for life beyond the solar system.

To examine the potential atmosphere of TRAPPIST-1e, the team had to wait until it crossed or "transited" the face of its parent star. This reveals details of the chemical composition of a planet's atmosphere because chemicals absorb light at characteristic wavelengths. That means when starlight passes through a planetary atmosphere, the chemicals in that atmosphere leave their characteristic "fingerprints" in the spectrum.

This isn't as straightforward as it may initially sound. Astronomers have to account for factors like starspots across the face of the red dwarf star. So the team has spent the last year carefully removing contamination from the TRAPPIST-1e data to hone in on the planet's atmosphere, or lack thereof.

"We are seeing two possible explanations," MacDonald said. "The most exciting possibility is that TRAPPIST-1e could have a so-called secondary atmosphere containing heavy gases like nitrogen. But our initial observations cannot yet rule out a bare rock with no atmosphere."

The indeterminate nature of the team's results means that JWST is far from finished with TRAPPIST-1e. The researchers hope to perform a deeper search for the planet's atmosphere, with each subsequent transit potentially presenting a clearer picture of its atmospheric contents.

"In the coming years, we will go from four JWST observations of TRAPPIST-1e to nearly 20," MacDonald concluded. "We finally have the telescope and tools to search for habitable conditions in other star systems, which makes today one of the most exciting times for astronomy."

The team's research was published as two papers on Monday (Sept. 8) in The Astrophysical Journal Letters

The sun will someday die. This will happen when it runs out of hydrogen fuel in its core and can no longer produce energy through nuclear fusion as it does now. The death of the sun is often thought of as the end of the solar system. But in reality, it may be the beginning of a new phase of life for all the objects living in the solar system.

When stars like the sun die, they go through a phase of rapid expansion called the Red Giant phase: The radius of the star gets bigger, and its color gets redder. Once the gravity on the star’s surface is no longer strong enough for it to hold on to its outer layers, a large fraction – up to about half – of its mass escapes into space, leaving behind a remnant called a white dwarf.

I am a professor of astronomy at the University of Wisconsin-Madison. In 2020, my colleagues and I discovered the first intact planet orbiting around a white dwarf. Since then, I've been fascinated by the prospect of life on planets around these, tiny, dense white dwarfs.

Researchers search for signs of life in the universe by waiting until a planet passes between a star and their telescope's line of sight. With light from the star illuminating the planet from behind, they can use some simple physics principles to determine the types of molecules present in the planet's atmosphere.

In 2020, researchers realized they could use this technique for planets orbiting white dwarfs. If such a planet had molecules created by living organisms in its atmosphere, the James Webb Space Telescope would probably be able to spot them when the planet passed in front of its star.

In June 2025, I published a paper answering a question that first started bothering me in 2021: Could an ocean – likely needed to sustain life – even survive on a planet orbiting close to a dead star?

A universe full of white dwarfs

A white dwarf has about half the mass of the Sun, but that mass is compressed into a volume roughly the size of Earth, with its electrons pressed as close together as the laws of physics will allow. The sun has a radius 109 times the size of Earth's – this size difference means that an Earth-like planet orbiting a white dwarf could be about the same size as the star itself.

White dwarfs are extremely common: An estimated 10 billion of them exist in our galaxy. And since every low-mass star is destined to eventually become a white dwarf, countless more have yet to form. If it turns out that life can exist on planets orbiting white dwarfs, these stellar remnants could become promising and plentiful targets in the search for life beyond Earth.

But can life even exist on a planet orbiting a white dwarf? Astronomers have known since 2011 that the habitable zone is extremely close to the white dwarf. This zone is the location in a planetary system where liquid water could exist on a planet’s surface. It can’t be too close to the star that the water would boil, nor so far away that it would freeze.

The habitable zone around a white dwarf would be 10 to 100 times closer to the white dwarf than our own habitable zone is to our Sun, since white dwarfs are so much fainter.

The challenge of tidal heating

Being so close to the surface of the white dwarf would bring new challenges to emerging life that more distant planets, like Earth, do not face. One of these is tidal heating.

Tidal forces – the differences in gravitational forces that objects in space exert on different parts of a nearby second object – deform a planet, and the friction causes the material being deformed to heat up. An example of this can be seen on Jupiter's moon Io.

The forces of gravity exerted by Jupiter's other moons tug on Io's orbit, deforming its interior and heating it up, resulting in hundreds of volcanoes erupting constantly across its surface. As a result, no surface water can exist on Io because its surface is too hot.

In contrast, the adjacent moon Europa is also subject to tidal heating, but to a lesser degree, since it's farther from Jupiter. The heat generated from tidal forces has caused Europa's ice shell to partially melt, resulting in a subsurface ocean.

Planets in the habitable zone of a white dwarf would have orbits close enough to the star to experience tidal heating, similar to how Io and Europa are heated from their proximity to Jupiter.

This proximity itself can pose a challenge to habitability. If a system has more than one planet, tidal forces from nearby planets could cause the planet’s atmosphere to trap heat until it becomes hotter and hotter, making the planet too hot to have liquid water.

Enduring the red giant phase

Even if there is only one planet in the system, it may not retain its water.

In the process of becoming a white dwarf, a star will expand to 10 to 100 times its original radius during the red giant phase. During that time, anything within that expanded radius will be engulfed and destroyed. In our own solar system, Mercury, Venus and Earth will be destroyed when the Sun eventually becomes a red giant before transitioning into a white dwarf.

For a planet to survive this process, it would have to start out much farther from the star — perhaps at the distance of Jupiter or even beyond.

If a planet starts out that far away, it would need to migrate inward after the white dwarf has formed in order to become habitable. Computer simulations show that this kind of migration is possible, but the process could cause extreme tidal heating that may boil off surface water – similar to how tidal heating causes Io’s volcanism. If the migration generates enough heat, then the planet could lose all its surface water by the time it finally reaches a habitable orbit.

However, if the migration occurs late enough in the white dwarf's lifetime – after it has cooled and is no longer a hot, bright, newly formed white dwarf – then surface water may not evaporate away.

Under the right conditions, planets orbiting white dwarfs could sustain liquid water and potentially support life.

Search for life on planets orbiting white dwarfs

Astronomers haven't yet found any Earth-like, habitable exoplanets around white dwarfs. But these planets are difficult to detect.

Traditional detection methods like the transit technique are less effective because white dwarfs are much smaller than typical planet-hosting stars. In the transit technique, astronomers watch for the dips in light that occur when a planet passes in front of its host star from our line of sight. Because white dwarfs are so small, you would have to be very lucky to see a planet passing in front of one.

Nevertheless, researchers are exploring new strategies to detect and characterize these elusive worlds using advanced telescopes such as the Webb telescope.

If habitable planets are found to exist around white dwarfs, it would significantly broaden the range of environments where life might persist, demonstrating that planetary systems may remain viable hosts for life even long after the death of their host star.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

That strong, baffling radio episode was captured by Ohio State University's Search for Extraterrestrial Intelligence (SETI) project, also known as the "Big Ear." It has been viewed by some as one of the oddest radio transmissions from afar ever detected, also cited as compelling evidence for extraterrestrial intelligence.

The outburst was a strong narrowband radio signal received on Aug. 15, 1977 by Ohio State University's Big Ear radio telescope. Astronomer Jerry Ehman discovered the anomaly a few days later while reviewing the recorded data — writing on a computer printout "Wow!"

Unpublished observations, archival data

Jump ahead to today. Researchers from the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo are proposing a less extraterrestrial explanation. On-going assessments, led by Abel Méndez, are being pursued under the "Arecibo Wow!" Project, an initiative established to analyze unexplained radio signals from space in the search for extraterrestrial intelligence.

"We look at old archives with modern science methodologies. It's a bit like space archaeology," said Wow! Signal researcher Hector Socas Navarro, director of the European Solar Telescope Foundation and a staff scientist at the Instituto de Astrofísica de Canarias.

New clues

Researchers from that project have re-analyzed decades of previously unpublished observations and archival data from the Ohio State University SETI program. The result is the most precise characterization yet of the perplexing signal from afar and revealing new clues to its origin.

"Our newly derived properties may help finally pinpoint the source of the Wow! Signal," Méndez told Space.com. While the group's just-published paper focused on revising the known properties of the Wow! Signal, "we also discovered new properties that we look forward to sharing in an upcoming paper," he advised.

"We aim to archive and share all data from the Big Ear telescope by 2027, marking the 50th anniversary of the Wow! Signal," Méndez added.

Natural astrophysical origin?

In a recent posting on the Arecibo Wow! Project's website, Méndez underscored the team's output to date.

The research findings spotlight the prospect that the Wow! Signal was created by a natural astrophysical origin, Méndez and colleagues report. Also the work does make radio interference "an increasingly unlikely explanation," they add.

"This study doesn't close the case," Méndez points out. "It reopens it, but now with a much sharper map in hand."

Méndez and fellow researchers hypothesize that the Wow! Signal was caused by a sudden brightening of the hydrogen line in interstellar clouds, triggered by a powerful transient radiation source such as a magnetar flare or soft gamma repeater (SGR).

"Our results don't solve the mystery of the Wow! Signal," Méndez states. "But they give us the clearest picture yet of what it was and where it came from. This new precision allows us to target future observations more effectively than ever before."

Citizen science — join the search

The continuing research into the Wow! Signal has spurred the creation of the Wow@Home project. This initiative is a low-cost way that others can now actively search for similar signals and other rare cosmic events, including potential technosignatures of other star folk — in real time.

Wow@Home project officials found that the Wow! Signal was strong enough that even small telescopes could potentially detect similar signals.

Indeed, a network of small radio telescopes offers several distinct advantages compared to large professional observatories.

Low-cost systems can operate autonomously around the clock, "making them ideal for continuous monitoring of transient events or long-duration signals that professional telescopes cannot commit to observing full-time," Méndez and colleagues suggest.

Wow-like signal strength

Wow@Home is a cost-effective, engaging, and accessible, ideal for education, citizen science, and expanding participation in radio astronomy.

"A complete setup costs around $500, including a dedicated computer, but we are not selling these systems. Instead, we will provide recommendations for the necessary parts and offer free software to power the telescope and connect it to the Wow@Home network to search for transient events," a Wow@Home posting explains.

The software is built on analysis methods the project's developing to detect Wow-like signals in the archive data of professional observatories, as part of their Arecibo Wow! undertaking.

For more information on Wow@Home, visit the project's website. The group's recent research report is available on arXiv.org and will be submitted to the Astrophysical Journal.

"We consider water to be required for life because that is what's needed for Earth life. But if we look at a more general definition, we see that what we need is a liquid in which metabolism for life can take place," study leader Rachana Agrawal, a postdoctoral student at the Massachusetts Institute of Technology (MIT), said in a statement.

Agrawal and her team studied ionic liquids — salts that are liquid at sub-boiling temperatures (below 212 degrees Fahrenheit, or 100 degrees Celsius) — as a potential hospitable environment for life. Per the researchers' laboratory experiments, ionic liquids can likely form from ingredients found on rocky planets and moons.

Most importantly, the team determined that ionic liquids could form where liquid water can't, thanks to its ability to remain liquid at a wide range of temperatures and pressures. And ultimately, these ionic liquids might be able to support biomolecules like proteins.

"[T]his can dramatically increase the habitability zone for all rocky worlds," said Agrawal.

As things go in science, this discovery was something of a happy accident. Initially, the team set out to investigate signs of life on Venus, looking to find a way to collect and evaporate sulfuric acid from Venus' clouds. But when the researchers ran their evaporation experiments, they found that a liquid layer always remained. That layer, they determined, was an ionic liquid, formed when sulfuric acid reacted with glycine.

"From there, we took the leap of imagination of what this could mean," said Agrawal. "Sulfuric acid is found on Earth from volcanoes, and organic compounds have been found on asteroids and other planetary bodies. So, this led us to wonder if ionic liquids could potentially form and exist naturally on exoplanets."

More study is necessary, of course. "We just opened up a Pandora's box of new research," said MIT professor Sara Seager, a co-author of the study. "It's been a real journey."

The team's paper was published Monday (Aug. 11) in the journal Proceedings of the National Academy of Sciences.

Using the Atacama Large Millimeter/ submillimeter Array (ALMA), a system of radio telescopes in Chile, the team detected traces of 17 complex organic molecules in the protoplanetary disc of V883 Orionis, a young star located around 1,305 light-years away in the constellation of Orion.

V883 Orionis is an infant star, or protostar, that is estimated to be just 500,000 years old, and it's in the active phase of gathering mass and forming planets. If 0.5 million years old seems ancient, consider that our middle-aged sun is about 4.6 billion years old.

Complex organic molecules are molecules that have more than five atoms, at least one of which is carbon. They have been seen around sites of star and planet formation previously.

However, the compounds discovered around V883 Orionis include the first tentative detections of ethylene glycol and glycolonitrile, compounds that are considered precursors to the building blocks of life. For instance, glycolonitrile is a precursor of the amino acids glycine and alanine, as well as the nucleobase adenine, one of the building blocks of DNA and RNA.

The find could therefore provide a missing link in the story of the evolution of molecules around young stars, accounting for the period between the initial formation of stars and the growth of planets in their surrounding protoplanetary disks.

"Our finding points to a straight line of chemical enrichment and increasing complexity between interstellar clouds and fully evolved planetary systems," team leader Abubakar Fadul, a scientists at the Max Planck Institute for Astronomy (MPIA) in Germany, said in a statement.

A cosmic chemical assembly line

Stars start life when overdense clumps in vast clouds of interstellar gas and dust collapse under their own gravity. This creates a protostar that continues to gather matter from its natal envelope until it has sufficient mass to trigger the fusion of hydrogen to helium in its core. That's the nuclear process that defines what a main-sequence star is.

As this proceeds, material around the budding star flattens out into a swirling donut of gas and dust called a protoplanetary disk, from which planets will eventually emerge.

The transition from protostar to a young main-sequence star is a violent one, replete with intense radiation, shocked gas, and gas being ejected from the protoplanetary disk. This is thought to be deleterious to the continued existence of complex chemicals built during earlier stages of the protostar's existence.

This has led to the development of a so-called "reset scenario" that sees the chemicals needed for life forming at later stages in the existence of the protoplanetary disk, as planets, asteroids, and comets are formed.

However, the new discovery suggests that this reset scenario is unnecessary.

"Now it appears the opposite is true," said team member and MPIA scientist Kamber Schwarz. "Our results suggest that protoplanetary disks inherit complex molecules from earlier stages, and the formation of complex molecules can continue during the protoplanetary disk stage."

The team theorizes that the period between the energetic protostellar phase and the establishment of a protoplanetary disk would be too brief for complex organic molecules to form in detectable amounts. The upshot of this is that the conditions that predefine biological processes may not be restricted to individual planetary systems, but may be more widespread.

Because the chemical reactions that create complex organic molecules proceed better in colder conditions, they could occur in icy dust that later gathers to form large bodies.

That means these molecules could remain hidden in dust, rock and ice in young planetary systems, only accessible when heating by the central star warms those materials.

This is something seen in our own solar system when comets from the outer region of our planetary system pass close to the sun, creating cometary tails and halos called comas.

Though V883 Orionis hasn't yet reached the mass needed to achieve nuclear fusion, there is a heating mechanism available in this young system for a similar thawing to occur: When material falls to the star, facilitating its growth, bursts of intense radiation are triggered.

"These outbursts are strong enough to heat the surrounding disk as far as otherwise icy environments, releasing the chemicals we have detected," said Fadul.

It's fitting that ALMA, an array of 66 radio telescopes located in the Atacama Desert region of northern Chile, has been integral to probing deeper into the disk around V883 Orionis. It was this array, after all, that first discovered the water snow line in the disk of V883 Orionis back in 2016.

"While this result is exciting, we still haven't disentangled all the signatures we found in our spectra," Schwarz said. "Higher resolution data will confirm the detections of ethylene glycol and glycolonitril and maybe even reveal more complex chemicals we simply haven't identified yet."

Fadul suggested that astronomers need to look at light from stars like V883 Orionis and its protoplanetary disk in other wavelengths of the electromagnetic spectrum to find even more evolved molecules.

"Who knows what else we might discover?" Fadul concluded.

The team's research is available as a preprint on the paper repository arXiv.

While signs of life on the world have failed to conclusively present themselves to the James Webb Space Telescope (JWST), the powerful space telescope has discovered that this planet is so rich in liquid water that it could be an ocean, or "Hycean" world.

"This has certainly increased the chances of habitability on K2-18 b" Nikku Madhusudhan, the University of Cambridge scientist behind the original K2-18b discovery as well as the new study, told Space.com. "This is a very important development and further increases the chance of a Hycean environment in K2-18 b. It confirms K2-18 b to be our best chance to study a potential habitable environment beyond the solar system at the present time."

The story regarding the habitability of K2-18 b began back in April 2025, when Madhusudhan and fellow researchers from the University of Cambridge announced they had found what they called the "strongest evidence yet" of life beyond the solar system around this distant super-Earth (it's around nine times as massive as our planet).

The evidence came from the tentative detection of molecules that, when found in the atmosphere of Earth, are typically the result of biological processes of living things. The pressure was then on to confirm these potential biosignatures: dimethyl sulfide and dimethyl disulfide.

The team set about this by observing four separate instances of K2-18 b crossing, or "transiting," the face of its parent red dwarf star, located about 124 light-years away, during its roughly 33-Earth-day orbit. Because chemicals absorb and emit light at characteristic wavelengths, when light from a parent star passes through a planet's atmosphere, the molecules in that atmosphere leave their telltale fingerprints in the spectrum of starlight.

"With four additional transit observations using JWST, we have measured the spectrum of K2-18 b’s atmosphere with unprecedented precision," Renyu Hu, the new study's team leader and a NASA Jet Propulsion Lab scientist, told Space.com. "The spectrum allowed us to conclusively detect both methane and carbon dioxide in the planet's atmosphere and to constrain their abundances. This information points to a planet with a water-rich interior."

Hu explained that the team searched for signals of dimethyl sulfide and other organic sulfur molecules in the spectrum using several independent models, but did not find conclusive evidence for their presence.

"This was not necessarily disappointing," Hu continued. "We're excited about establishing the planet’s water-rich nature."

Is K2-18 b a ocean world?

Saying it's now confirmed that K2-18 b is water-rich, Hu explained that the next step is to discover if the planet possesses a global liquid water ocean.

Ironically, one of the most positive signs of such an ocean is the fact that the atmosphere of this super-Earth appears to lack water vapor.

"The spectrum we obtained does not show signs of water vapor. If the atmosphere truly lacks water, this suggests that water has been depleted — most likely through condensation," Hu said. "On Earth, this process is known as the 'cold trap,' and geoscientists consider it essential for retaining water over billions of years by preventing it from escaping to space.

"Observing a similar process on an exoplanet would be very exciting. Rigorously confirming the absence of water can by itself be a scientifically important goal for future observations," Hu said.

However, Hu cautioned that the spectrum detected by the JWST could also be explained by an alternative model in which the atmosphere actually contains abundant water vapor.

Establishing whether K2-18 b and other similar temperate, sub-Neptune-sized planets possess liquid water oceans, Hu says, will also require detecting the presence of a broader set of atmospheric gases beyond methane and carbon dioxide. It would also require an absence of molecules like ammonia, carbon monoxide and sulfur dioxide, which, as of yet, have indeed not been detected in the atmosphere of K2-18 b

"This conclusion is based on theoretical work by my group and several others," Hu added. "With the new observations providing valuable context, we've summarized these insights into a roadmap to help guide future observations and studies."

Meanwhile, the search for the biosignatures, dimethyl sulfide and dimethyl disulfide, is far from done; while not hitting the significance level required for a confirmation, this research did provide a stronger signal from these molecules than were provided by previous examinations.

"The evidence for dimethyl sulfide in the present work is significantly higher than what we had with our previous observations in the same near-infrared wavelength range," Madhusudhan said. "However, this evidence is still not high enough to claim a conclusive detection.

"We also need to be able to distinguish dimethyl sulfide from other possible contributors, such as methyl mercaptan, which is also a biosignature on Earth."

It looks certain that K2-18 b will continue to hold the interest of astronomers for some time.

"It is great that we are able to infer tentative signs of potential biosignatures with current JWST observations, but significantly more time is needed for conclusive detections. A key question is whether the atmosphere contains one or more biosignatures," Madhusudhan said. "At the same time, extensive theoretical and experimental efforts are needed to robustly identify biological and non-biological pathways for candidate biosignature molecules."

One thing the team is sure of, though, is the progress made thus far in the study of K2-18 b wouldn't have been possible without the JWST. And, the $10 billion space telescope is set to play a key role in the future investigation of this super-Earth.

"Our observations and analyses add to the growing list of exciting discoveries that highlight the truly transformative science enabled by JWST," Hu concluded. "While we found its Near-Infrared Spectrograph [NIRSpec] particularly well suited to address the goals of our study, other JWST instruments or observational modes could provide complementary and highly valuable information to further enhance our understanding of this planet."

The team's research is available as a preprint on the paper repository arXiv.

Arsenic, as we know from its use as a poison, is a toxic substance. Thus, life as we know it of course would not include arsenic in its biochemistry. Yet, because the search for alien life is, by its very definition, a search for life as we don't know it, astrobiologists like to consider the possibility of organisms that have a different biochemistry to the one we're familiar with.

This, in fact, led to NASA, — and with great razzamatazz, one might add — holding a press conference in 2010 that declared the supposed discovery of arsenic-based microbial life in Mono Lake, which is a heavily salt-rich body of water in California.

NASA claimed this discovery would forever change the search for life beyond Earth.

Life's chemical details

Consider that all life as we know it, including human life, exclusively uses six key elements in its biochemistry: carbon, hydrogen, nitrogen, phosphorus, oxygen and sulfur.

Take phosphorus as an example. In our biochemistry, phosphorus, in the form of phosphate, is crucial for forming the sugar-phosphate backbone of molecules of RNA and DNA, as well as storing and delivering metabolic energy through adenosine triphosphate (ATP).

Astronomical observations, however, suggest phosphorus might not be evenly distributed across the Milky Way galaxy. And it has been posited that life in those phosphorus-depleted regions of space might survive by substituting phosphorus with another element, such as arsenic. It was this possibility that, 15 years ago, prompted a team led by Felisa Wolfe–Simon of NASA's Astrobiology Institute to search for possible arsenic-based life in the extreme alkaline conditions within Mono Lake.

Then, in that 2010 press conference, the discovery team revealed they had found it in the form of a bacterium known as GFAJ-1 present in supposedly phosphorus-free samples from Mono Lake. The discovery was hailed as a revolutionary development in astrobiology — for all of about five minutes.

Despite all the hullaballoo of the press conference, when Wolfe–Simon and her team's work was published online by the journal Science, other biochemists quickly came out to argue there were serious flaws in the research. Specifically, they argued that swapping out phosphorus for arsenic would cause DNA to dissolve within a second when exposed to water. More damning was the claim from the critics that the samples used by Wolfe–Simon's team were contaminated by phosphorus from the lake. The life in those samples, the critics argued, was probably still just using the phosphorus within those samples.

When Science finally published the research paper in print a year later, it was appended by eight technical comments from other researchers highly critical of the findings, plus two extra papers from independent teams who tried to replicate the results but failed to find any evidence for arsenic-based life in Mono Lake. Wolfe–Simon and her colleague also published a response to the criticisms, in which they wrote that "we maintain that our interpretation of As [arsenic] substitution, based on multiple congruent lines of evidence, is viable."

Not many people believed them, and Wolfe–Simon's team have never published the results of any follow-up experiments that try to address some of the points in the criticism; they also declined to respond to any criticism other than through the medium of peer-reviewed letters. The blowback against Wolfe–Simon's team was fierce and, at times, unsightly, with some abusive comments being leveled directly at Wolfe–Simon, who was still a young researcher. As a consequence, Wolfe–Simon opted to drop out of active research.

Now, 15 years later, Science's Editor-in-Chief Holden Thorp and the journal’s Executive Editor Valda Vinson have reopened the can of worms by deciding to retract the paper. Why has it taken so long for them to do so?

"Science did not retract the paper in 2012 because at that time, Retractions were reserved for the Editor-in-Chief to alert readers about data manipulation or for authors to provide information about post-publication issues," Science’s editors wrote in their official retraction notification. "Our decision then was based on the editors' view that there was no deliberate fraud or misconduct on the part of the authors. We maintain this view, but Science’s standards for retracting papers have expanded. If the editors determine that a paper's reported experiments do not support its key conclusions, even if no fraud or manipulation occurred, a Retraction is considered appropriate."

The other side of the story

Traditionally, papers were only retracted if evidence of fraud or misconduct came to light, or if a paper's authors requested that it be retracted, perhaps if new evidence disproved their results. However, the Retraction Watch website reports that, since 2019, Science has retracted 20 papers from its various publications, mostly on the basis of what the journal believes to be innocent errors.

Suffice to say, Wolfe–Simon and her team-members do not agree with Science's decision. In their response, published in the interests of fairness along with the retraction by Science, the team stated their disappointment.

"We do not support this retraction," they wrote. "While our work could have been written and discussed more carefully, we stand by the data as reported. These data were peer-reviewed, openly debated in the literature, and stimulated productive research."

Moreover, the team argues that Science's decision-making process was flawed and that it contravenes the guidelines of the Committee on Publication Ethics, or COPE. Those guidelines state that retraction is only warranted when there is clear evidence of major errors, the fabrication of data, or falsification that damages the reliability of a paper's findings.

"In going beyond COPE, the editors of Science explain that 'standards for retracting papers have expanded'," the team wrote. "We disagree with this standard, which extends beyond matters of research integrity. Disputes about the conclusions of papers, including how well they are supported by the available evidence, are a normal part of the process of science. Scientific understanding evolves through that process, often unexpectedly, sometimes over decades. Claims should be made, tested, challenged, and ultimately judged on the scientific merits by the scientific community itself."

Thorp and Vinson went further in a blog post on Science's website, where they were clearer on the reason for the retraction and arguing that COPE's guidelines allow them to retract the paper. "Given the evidence that the results were based on contamination, Science believes that the key conclusion of the paper is based on flawed data," they said.

The Retraction Watch website reports that Wolfe–Simon's team said that when they had been told about the retraction, they were not told that it was because of the claimed contamination. In fact, they only heard that from a second-hand source who had seen the blog post. Even so, contamination had been the number one criticism going all the way back to 2010, and was not a new or surprising accusation.

Thorp and Vinson ended their blog post by saying "we hope this decision brings the story to a close."

It remains to be seen whether this will be the case. However, what is clear is that there are serious lessons to be learned by both sides about how to present controversial results and how to both give and receive scientific criticism — Thorp and Vinson made a point in saying they condemn verbal abuse and ad hominem attacks that had been directed towards Wolfe–Simon and her team by other researchers. It also sheds light on the intricacies of when and how papers should be retracted.

In recent years, we have seen how claims of phosphine in the atmosphere of Venus and dimethyl sulphide, which is a potential biosignature, in the atmosphere of the exoplanet K2-18b have sparked debate and argument. It is to be hoped that scientists in the research community can remember to not take disagreements too far when debating these and other claimed discoveries in the future.

That's the theory of a team of researchers who looked at hundreds of extrasolar planets, or exoplanets, observed by NASA's Transiting Exoplanet Survey Satellite (TESS).

TESS hunts exoplanets by catching them as they cross the face of, or "transit," their parent star, which causes a tiny drop in light from that star. The study team discovered that light from stars neighboring the one being transited could "contaminate" TESS' data, making it look like the transiting planet is blocking less light than it actually is. And that would make the planet look smaller than it is.

"We found that hundreds of exoplanets are larger than they appear, and that shifts our understanding of exoplanets on a large scale," University of California, Irvine researcher and team leader Te Han said in a statement. "This means we may have actually found fewer Earth-like planets so far than we thought."

Exoplanets throw shade

Exoplanets are so distant and faint that it is only on rare occasions that astronomers can image them directly.

That means the transit method has become the most successful way of detecting worlds beyond the solar system. It requires the planet and its star to be at the right angle in relation to Earth, and for astronomers to wait for the planet to make two transits to confirm its existence.

The transit method is best at spotting short-period planets orbiting close to their host stars, because they make more frequent transits. The method also favors larger planets, which block more light.

"We’re basically measuring the shadow of the planet," said team member and UC Irvine astronomer Paul Robertson.

The team gathered hundreds of TESS observations of exoplanets, sorting them by the width of the exoplanets in question.

They then used computer modeling and data from the European Space Agency's (ESA) star-tracking mission Gaia to estimate how much light contamination TESS is experiencing during its observations.

"TESS data are contaminated, which Te's custom model corrects better than anyone else in the field," said Robertson. "What we find in this study is that these planets may systematically be larger than we initially thought. It raises the question: Just how common are Earth-sized planets?"

Move over Earth-like worlds: ocean planets could be more common

Because of the biases of the transit method mentioned above, the number of exoplanets detected with TESS having sizes and compositions similar to those of Earth was already low.

"Of the single-planet systems discovered by TESS so far, only three were thought to be similar to Earth in their composition," Han explained. "With this new finding, all of them are actually bigger than we thought."

The likely outcome of this is that those exoplanets are larger ocean planets or "hycean worlds" covered by a large single ocean. Those worlds could also be gas giants smaller than Jupiter, like Neptune and Uranus.

That impacts the search for life because, though hycean worlds are packed with water, they could be lacking other ingredients needed for life to arise.

"This has important implications for our understanding of exoplanets, including, among other things, prioritization for follow-up observations with the James Webb Space Telescope, and the controversial existence of a galactic population of water worlds," Roberston added.

The next step for Han, Roberston, and colleagues is to re-examine planets previously deemed uninhabitable due to their size, to see if they are larger than previously thought.

In the meantime, the research is a reminder to astronomers to be cautious when assessing TESS data.

The team's research was published on Monday (July 14) in the Astrophysical Journal Letters.

These lakes and Titan's seas are filled with liquid hydrocarbons like ethane and methane rather than water. And though we know water is a key ingredient of life on Earth, astrobiologists have theorized that Titan's liquid hydrocarbons could allow the molecules needed for life to form, whether that life is similar to what we see on Earth or a very different form of life.

This new research suggests a way vesicles could form on Titan based on what we know about its atmosphere and chemistry. The formation of such compartments is a key step on the road to the development of "protocells."

"The existence of any vesicles on Titan would demonstrate an increase in order and complexity, which are conditions necessary for the origin of life," Conor Nixon of NASA's Goddard Space Flight Center said in a statement.

"We're excited about these new ideas because they can open up new directions in Titan research and may change how we search for life on Titan in the future."

The path to life starts with pockets

The process of creating vesicles begins with molecules called amphiphiles, dual-nature molecules with both water-loving (hydrophilic) and water-repellent (hydrophobic) ends. Under certain conditions, these molecules can self-organize to create vesicles.

On Earth, when amphiphiles meet water, they group together to form spheres similar to soap bubbles with the water-loving end facing outwards, protecting the hydrophobic end.

If two layers of amphiphiles are together, they can form a bilayer "ball" with a shell of water sandwiched between the two layers of molecules. A structure that resembles a living cell.

This process would be very different on Titan due to its environment, one that is radically different than Earth's.

Titan isn't just the largest moon in the solar system; it is also the moon with the densest atmosphere. This is primarily because of Titan's cool temperature and its distance from the sun, which prevents its atmosphere from being stripped by the solar wind.

From 2004 to 2017, the Cassini spacecraft was able to stare through this substantial atmosphere to discover how the meteorological cycle of Titan has influenced its surface.

Though the majority of Titan's atmosphere is composed of nitrogen, its clouds are composed of methane that erodes the surface and river channels as it falls as rain and fills its lakes and seas. When exposed to sunlight, the methane evaporates and rises to the atmosphere again, regenerating Titan's clouds.

The activity of methane through Titan's atmosphere allows complex chemistry to happen, particularly when sunlight splits methane molecules, creating fragments that recombine as complex organic molecules.

This team theorizes that vesicles might form on Titan when sea-spray droplets are thrown into the atmosphere by methane raindrops landing on the surface of lakes and seas.

If the surfaces of Titan's seas are coated with layers of amphiphiles, the sea-spray droplets will be too. That means when those launched droplets fall back to the methane seas, they meet the amphiphile sea-layer and form a bilayer vesicle, enclosing the original droplet.

Over time, these vesicles could be dispersed through the lakes and seas, interacting and potentially leading to the creation of protocells.

The discovery is sure to generate excitement for NASA's forthcoming Dragonfly mission, which will set off for Titan in 2028. Arriving in 2034, the nuclear-powered rotocopter craft aims to explore prebiotic chemistry and habitability on the Saturnian moon.

Understanding this process as it occurs on Titan, if it is occurring, could shed light on the mystery of how life emerged on Earth.

The team's research was published on July 10 in the journal International Journal of Astrobiology.

"It's harder, but certainly not impossible, to live in these conditions," Christopher Glein, an ocean worlds scientist at the Southwest Research Institute (SwRI) in San Antonio told Space.com.

Cassini discovered Enceladus' plumes of water vapor, which jet out from large cracks in the icy surface called "tiger stripes" at the moon's southern polar region, in 2005. Although the Cassini mission, which ended in a blaze of glory in September 2017 when the orbiter plunged into Saturn, was not designed to sample material from such plumes, two of its instruments, the Cosmic Dust Analyzer and the Ion and Neutral Mass Spectrometer, were able to at least get a taste of them during close flybys of the icy moon. What they found offered clues as to the contents of the ocean deep within Enceladus that feeds the plumes.

"The payoff from Cassini far exceeded what it was designed to accomplish," said Glein. "We discovered a habitable ocean at Enceladus."

Those measurements remain our best study so far of any of the ocean moons of the outer solar system, and through geochemical modeling scientists are able to draw some conclusions. New research — by Glein and his SwRI colleague, planetary archaeologist Ngoc Truong — has determined that the pH of the ocean beneath Enceladus' ice is moderately high, between 10.1 and 11.6

The pH scale is a measure of how acidic or alkaline something is, 1 being highly acidic, 14 being highly alkaline, and 7 being neutral. Hence Enceladus' ocean is quite alkaline. For comparison, Earth's ocean has a pH of about 8.

The researchers arrived at this conclusion by studying the abundance and distribution of phosphate minerals in the ice grains within the plumes, in particular the ratio of mono-hydrogen phosphate (HPO4) to regular phosphate (PO4), which is a direct indicator of the pH level of the water. The range of possible pH that Glein and Truong found is higher than the previous estimates of 8 to 9. However, those estimates were made before 2023, when further detailed analysis of Cassini's data revealed high concentrations of phosphates in the plumes.

The alkalinity is a signature of interactions between water and iron-, magnesium- and sodium-bearing silicate rock on the ocean floor. These water-rock interactions release sodium hydroxide (NaOH) into the ocean that subsequently reacts with carbon dioxide and produces the high alkalinity.

"One consequence of these conditions is a high carbonate alkalinity, which supercharges the solubility of calcium phosphate minerals — like apatite. Your teeth might dissolve in Enceladus' ocean," said Glein.

Such high alkalinity would be somewhat challenging for life. "High pH tends to break apart biological polymers," said Glein when asked by Space.com. "However, we know that some microbes on Earth can tolerate the range of pH found on Enceladus."

These terrestrial, alkaline-loving microbes are extremophiles called alkaliphiles. And there's another boost for the possibility of life in Enceladus' ocean, since the water-rock interactions produce minerals and ions that can be used by microbial life for energy and sustenance. The conditions even provide clues as to where in the ocean we might find such life, should it exist there.

"Metals become less soluble at higher pH, so iron may be scarce in Enceladus' ocean," said Glein. "I think the best place to live would be at the seafloor. If you're a microbe, you could directly 'mine' iron and other metals from minerals without relying on solubility. We might want to think about biofilms on Enceladus."

Based on the alkalinity, the chemical composition of the plumes as measured by Cassini and the expected minimal outgassing of carbon dioxide from the ocean, Glein and Truong have assembled a list of minerals and molecules that we could expect to find in Enceladus' ocean. The most abundant compounds on the list are sodium, chlorine, sodium carbonate, carbonate ions, ammonia and potassium ions.

"The composition does make sense for deep circulation of ocean water through the rocky core of Enceladus," said Glein.

One surprise was the inferred high abundance of molecular hydrogen (H2). However, its concentration is similar to some deep-sea environments on Earth, such as the vast field of hydrothermal vents in iron-rich rocks called the "Lost City" deep in the Atlantic Ocean.

"There, H2 supports life by supplying a source of chemical energy," said Glein.

Although the list of mineral constituents in the ocean is not confirmed — we'd have to return to Enceladus to do that — it just shows that we don't need to venture into the depths of the dark water to learn the ocean's secrets. Just flying through the plumes is enough to give us a good indication. Cassini did so without specialized equipment for analyzing molecules and compounds within the plumes, since when it was launched (October 1997) the plumes had not even been discovered. Glein thirsts to return with a dedicated mission carrying state-of-the-art instruments specifically designed for the job.

"Imagine what we could find," he mused. "The picture for Enceladus is of an ocean that is intensely affected by water-rock interactions. Enceladus is a geochemical paradise!"

Glein and Truong's findings were published online June 20 in the journal Icarus.

Grandiose headlines often promise proof that we are not alone, but scientists remain cautious. Is this caution unique to the field of astrobiology? In truth, major scientific breakthroughs are rarely accepted quickly.

Newton’s laws of motion and gravity, Wegener’s theory of plate tectonics, and human-made climate change all faced prolonged scrutiny before achieving consensus.

But does the nature of the search for extraterrestrial life mean that extraordinary claims require even more extraordinary evidence? We’ve seen groundbreaking evidence in this search beforehand, from claims of biosignatures (potential signs of life) in Venus’s atmosphere to NASA rovers finding “leopard spots” – a potential sign of past microbial activity – in a Martian rock.

Both stories generated a public buzz around the idea that we might be one step closer to finding alien life. But on further inspection, abiotic (non-biological) processes or false detection became more likely explanations.

In the case of the exoplanet, K2-18 b, scientists working with data from the James Webb Space Telescope (JWST) announced the detection of gases in the planet’s atmosphere – methane, carbon dioxide, and more importantly, two compounds called dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). As far as we know, on Earth, DMS/DMDS are produced exclusively by living organisms.

Their presence, if accurately confirmed in abundance, would suggest microbial life. The researchers even suggest there’s a 99.4% probability that the detection of these compounds wasn’t a fluke – a figure that, with repeat observations, could reach the gold standard for statistical certainty in the sciences. This is a figure known as five sigma, which equates to about a one in a million chance that the findings are a fluke.

So why hasn’t the scientific community declared this the discovery of alien life? The answer lies in the difference between detection and attribution, and in the nature of evidence itself.

JWST doesn’t directly “see” molecules. Instead, it measures the way that light passes through or bounces off a planet’s atmosphere. Different molecules absorb light in different ways, and by analysing these absorption patterns – called spectra – scientists infer what chemicals are likely to be present. This is an impressive and sophisticated method – but also an imperfect one.

It relies on complex models that assume we understand the biological reactions and atmospheric conditions of a planet 120 light years away. The spectra suggesting the existence of DMS/DMDS may be detected because you cannot explain the spectrum without the molecule you’ve predicted, but it could also result from an undiscovered or misunderstood molecule instead.

Climate comparison

Given how momentous the conclusive discovery of extraterrestrial life would be, these assumptions mean that many scientists err on the side of caution. But is this the same for other kinds of science? Let’s compare with another scientific breakthrough: the detection and attribution of human-made climate change.

The relationship between temperature and increases in CO₂ was first observed by the Swedish scientist Svante Arrhenius in 1927. It was only taken seriously once we began to routinely measure temperature increases. But our atmosphere has many processes that feed CO₂ in and out, many of which are natural.

So the relationship between atmospheric CO₂ and temperature may have been validated, but the attribution still needed to follow.

Carbon has three so-called flavors, known as isotopes. One of these isotopes, carbon-14, is radioactive and decays slowly. When scientists observed an increase in atmospheric carbon dioxide but a low volume of carbon-14, they could deduce that the carbon was very old – too old to have any carbon-14. Fossil fuels – coal, oil and natural gas – are composed of ancient carbon and thus are devoid of carbon-14.

So the attribution of anthropogenic climate change was proven beyond reasonable doubt, with 97% acceptance among scientists. In the search for extraterrestrial life, much like climate change, there is a detection and attribution phase, which requires the robust testing of hypotheses and also rigorous scrutiny.

In the case of climate change, we had in situ observations from many sources. This means roughly that we could observe these sources close up. The search for extraterrestrial life relies on repeated observations from the same sensors that are far away. In such situations, systematic errors are more costly.

Further to this, both the chemistry of atmospheric climate change and fossil fuel emissions were validated with atmospheric tests under lab conditions from 1927 onwards. Much of the data we see touted as evidence for extraterrestrial life comes from light years away, via one instrument, and without any in situ samples.

The search for extraterrestrial life is not held to a higher standard of scientific rigor but it is constrained by an inability to independently detect and attribute multiple lines of evidence.

For now, the claims about K2-18 b remain compelling but inconclusive.

That doesn’t mean we aren’t making progress. Each new observation adds to a growing body of knowledge about the universe and our place in it. The search continues – not because we’re too cautious, but because we are rightly so.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

That's according to scientists who have found that lichen in the Mojave Desert managed to survive for 3 months under levels of intense radiation from the sun that had previously been considered lethal to this organism.

While the lichen was badly damaged, it was able to recover and eventually replicate. That indicates to scientists that other extraterrestrial life that requires photosynthesis could prosper on terrestrial or rocky extrasolar planets, or "exoplanets," even if they are exposed to radiation from their own star that had previously been considered deadly.

"The study was motivated by a curious observation," team member and Desert Research Institute scientist Henry Sun said in a statement. "I was just walking in the desert, and I noticed that the lichens growing there aren't green, they're black. They are photosynthetic and contain chlorophyll, so you would think they'd be green.

"So I wondered, 'What is the pigment they're wearing?' And that pigment turned out to be the world's best sunscreen."

Lichen is composed of algae or cyanobacteria that exist symbiotically with fungi. The lichen that formed the basis of this research is Clavascidium lacinulatum, or the "common lichen," found in arid regions across the globe, including Europe, Asia, North Africa, and, of course, the U.S.

Common lichen. Not so common sunscreen

Life on Earth thrives on light from the sun, which plants and other life forms use to create sugars via photosynthesis. But sunlight is a mix of electromagnetic radiation of different wavelengths, and some of this radiation is not so useful to life; in particular, ultraviolet light.

Terrestrial organisms have evolved to cope with Ultraviolet A (UVA) radiation and less common UVB radiation. In humans, UVA is associated with skin aging and wrinkle formation, while UVB causes skin damage like tanning, sunburn, and can even lead to skin cancer.

However, light that leaves our star also contains UVC radiation, which has a shorter wavelength than UVA or UVB light and carries more energy, making it much more harmful to life, damaging DNA, and preventing reproduction. In fact, UVC is so lethal that it can be used to sterilize air and water, wiping out microorganisms like bacteria and viruses.

Fortunately, our atmosphere filters out much of the ultraviolet light blasted at us from the sun, protecting life from its harshest effects. UVC radiation is completely absorbed, meaning it doesn't reach the surface of our planet. But terrestrial worlds in other star systems may not be so lucky.

This could be especially detrimental to life around so-called M-class and F-class stars, which are hotter and brighter than the sun and are known to belt out intense UVC radiation, especially during stellar flares.

"After the launch of the James Webb Space Telescope (JWST), which can see extremely far into space, the excitement shifted from finding life on Mars to these exoplanets," Sun said. "We're talking about planets that have liquid water and an atmosphere."

Sun and colleagues wanted to see how lichen coped with bombardment by UVC radiation, so they placed a sample next to a UVC lamp for 3 months in a controlled setting.

"In order for a microorganism to persist on a planet, it has to last longer than a day," Sun explained. "So, our experiment had to be long enough to be ecologically significant. We also wanted to go beyond just activity and demonstrate viability."

To their surprise, half the cells comprising the lichen regained the ability to replicate after water was reintroduced to them.

After further investigation with chemists from the University of Nevada, Sun and colleagues found that this is because the acids of the lichen are akin to nature's version of the additives used to make plastics UV-resistant.

Diving deeper, the team cut through the lichen, finding that the top layer was darker, almost like a suntan in humans. Furthermore, they found that when the fungi and the algae that make up lichen were separated, the algae died within minutes of UVC exposure.

The team surmised that because lichen isn't regularly exposed to UVC thanks to Earth's atmosphere, its protective layer evolved as a bonus of its UVA and UVB shielding rather than as an aid to survival.

"We came to the conclusion that the lichen's top layer—a less than millimeter thick skin, if you will—assures that all the cells below are protected from radiation," Sun continued. "This layer acts as a photostabilizer and even protects the cells from harmful chemical reactions caused by the radiation, including reactive oxygen."

As for this discovery's implications for life on other worlds, the team posits that some exoplanets may "be teeming with colonial microorganisms that, like the lichens in the Mojave Desert, are 'tanned' and virtually immune to UVC stress."

"This work reveals the extraordinary tenacity of life even under the harshest conditions, a reminder that life, once sparked, strives to endure," team leader and NASA Goddard Space Flight Center researcher Tejinder Singh said. "In exploring these limits, we inch closer to understanding where life might be possible beyond this planet we call home."

The team's research was published on June 12 in Astrobiology

The signs were rooted in a tentative detection of dimethyl sulfide (DMS) — a molecule produced on Earth solely by marine life — and/or its close chemical relative DMDS, which is also a potential biosignature, in the atmosphere of the exoplanet. This finding, along with the possibility that K2-18b is a "Hycean world" with a liquid water ocean, sparked significant interest about its potential to support life.

However, these results have sparked intense debate among astronomers. While recognizing this finding would be a groundbreaking achievement and a major testament to the James Webb Space Telescope's (JWST) capabilities if true, many scientists remain skeptical, questioning both the reliability of the detected DMS signature as well as whether DMS itself is a dependable sign of life in the first place. As such, many independent teams have been conducting follow-up studies about the original claims — and a newly published one only adds to the debate, suggesting the Cambridge scientists' DMS detection wasn't significant enough to warrant the publicity it received.

"Among the physical sciences, astronomy enjoys a privileged position," Rafael Luque, a post doctoral researcher at the University of Chicago, told Space.com. "It is more frequently covered in the media thanks to its visual appeal and the big philosophical and universal questions it addresses. It was therefore expected that — even if tentative — the detection of a potential biomarker in the atmosphere of an exoplanet would have extensive coverage."

The significance of significance

Luque and his colleagues, including fellow postdoctoral researchers Caroline Piaulet-Ghorayeb and Michael Zhang, remain unconvinced that what astronomers observed on K2-18b was in fact a credible signature indicating life. In a recent arxiv preprint — which is yet to be peer-reviewed — their team re-examined the validity of the original evidence. "This is how science works: evidence and counterevidence go hand in hand,” he stated.

When scientists study data from different instruments separately, they might end up with conflicting results — it's like finding two different "stories" about a subject that don't match. "This is, in fact, what happened in the original team's papers," Zhang told Space.com. "They inferred a much higher temperature from their MIRI (mid-infrared) data than from their NIRISS and NIRSpec (near-infrared) data. Fitting all the data with the same model ensures that we're not telling contradictory stories about the same planet."

Thus, the team conducted a joint analysis of K2-18b using data from all three of the JWST's key instruments — the Near Infrared Imager and Slitless Spectrograph (NIRISS) and the Near Infrared Spectrograph (NIRSpec), which capture near-infrared light, and the Mid-Infrared Instrument (MIRI), which detects longer mid-infrared wavelengths. The goal was to ensure a consistent, planet-wide interpretation of K2-18b's spectrum that the team felt the original studies both lacked.

"We reanalyzed the same JWST data used in the study published earlier this year, but in combination with other JWST observations of the same planet published […] two years ago," Piaulet-Ghorayeb told Space.com. "We found that the stronger signal claimed in the 2025 observations is much weaker when all the data are combined."

These signals may appear weaker when all data is combined because the initial "strong" detection may have been overestimated, the team says, due to being based on a limited initial data set. Combining data from multiple sources lets scientists cross-check and verify the strength — and validity — of a particular signal.

"Different data reduction methods and retrieval codes always give slightly different results, so it is important to try multiple methods to see how robust the results are," explained Piaulet-Ghorayeb. "We never saw more than insignificant hints of either DMS or DMDS, and even these hints were not present in all data reductions."

"Importantly, we showed that when testing a wider range of molecules that we expect to be produced abiotically in the atmosphere, the same observed spectral features can be reproduced without the need for DMS or DMDS," she continued.

More than one path to a result

Molecules in an exoplanet's atmosphere are typically detected through spectral analysis, which identifies unique "chemical fingerprints" based on how the planet's atmosphere absorbs specific wavelengths of starlight as it passes — or transits — in front of its host star. This absorption leaves distinct patterns in the light spectrum that reveal the presence of different molecules.

"Each molecule’s signature is unique, but different molecules can have some features that fall in similar places because of their close molecular structures," explained Piaulet-Ghorayeb.

The difference between DMS and ethane — a common molecule in exoplanet atmospheres — is just one sulfur atom, and current spectrometers, including those on the JWST, have impressive sensitivity, but still face limits. The distance to exoplanets, the faintness of signals, and the complexity of atmospheres mean distinguishing between molecules that differ by just one atom is extremely challenging.

"It is widely recognized as a huge problem for biomarker detection, though not an insurmountable one, because different molecules do have subtly different absorption features," said Piaulet-Ghorayeb. "Until we can separate these signals more clearly, we have to be especially careful not to misinterpret them as signs of life."

Beyond technical limitations, another source of skepticism is how the data has been interpreted statistically. Luque points out that the 2023 study described the detection of DMS as "tentative," reflecting the preliminary nature of the finding. However, the most recent 2025 paper reported that the detection of DMS and/or DMDS reached 3-sigma significance — a level that, while below the 5-sigma threshold required for a confirmed discovery, is generally considered moderate statistical evidence.

"Surprisingly, this latest work was used to double down on the claim for DMS and even more complex molecules to be present. The detection, however, is not statistically significant nor robust, as we show in our work.

Despite these uncertainties, the team is worried that media coverage has continued to spotlight bold claims about DMS and other molecules. "The [JWST] telescope is incredibly powerful, but the signals we're detecting are very small. As a community, we have to make sure that any claims we make about a planet’s composition are robust to the choices made when processing the data from the telescope," said Piaulet-Ghorayeb.

"Researchers have the responsibility to double-check and verify, but the media is also responsible for duly reporting these follow-up works to the general public," added Luque. "Even if they have less catchy titles."

"As Carl Sagan once said, 'extraordinary claims require extraordinary evidence,'" said Luque. "That threshold was not met by how the results were disseminated to the general public."

Whether we'll ever get a clear answer about life on K2-18 b is uncertain — not just because of technological limits, but because the case for follow-ups with the JWST may simply not be strong enough. "JWST is continuing to observe K2-18b, and even though the new observations won't have the ability to detect life, we will soon find out more about the planet's atmosphere and interior," Zhang said.

Recently, the Coller Dolittle Challenge awarded the winner of its first $100,000 annual prize to accelerate progress toward interspecies two-way communication. A prize of equal value will be awarded every year until a team deciphers the secret to interspecies communication.

This year's winning team of researchers has discovered that dolphin whistles could function like words — with mutually understood, context-specific meaning.

Crack the code

The winning team was led by Laela Sayigh from the Woods Hole Oceanographic Institution. The researchers are studying the resident bottlenose dolphin community offshore of Sarasota, Florida.

They were on the lookout for "non-signature" whistles, which comprise approximately 50% of the whistles produced by Sarasota dolphins. Non-signature whistles differ from the more widely studied "signature" whistles, which are referential, name-like vocalizations.

Sayigh's team used non-invasive suction-cup hydrophones, which they placed on the dolphins during unique catch-and-release health assessments, as well as digital acoustic tags.

"Bottlenose dolphins have long fascinated animal communication researchers," Sayigh said in a statement. "Our work shows that these whistles could potentially function like words, shared by multiple dolphins."

Sayigh and her team can now use deep learning in an attempt to "crack the code" and analyze those whistles.

Zoologist's guide to the galaxy

But what does all this have to do with E.T.?

"My interests are very firmly here on Earth, in learning about how dolphins communicate with each other," Sayigh told Space.com "I do know that there are others in the animal communication world that are interested in this, however."

One of those researchers is Arik Kershenbaum, an associate professor and director of studies at Girton College, part of the University of Cambridge in England. He's the author of "The Zoologist's Guide to the Galaxy: What Animals on Earth Reveal About Aliens — and Ourselves" (Viking, 2020).

Kershenbaum explained that the book is about life on Earth, because "that's all we have to look at." He also contributed a white paper for a workshop at the Search for Extraterrestrial Intelligence (SETI) Institute in California, titled "What Animal Studies Can Tell Us about Detecting Intelligent Messages from Outside Earth."

Cross-species database

In that paper for the SETI Institute, Kershenbaum and colleagues concluded that animal communication research is the closest we are likely to get to studying extraterrestrial signals, until such signals are actually received.

"Many of the challenges facing SETI research are similar to those already addressed in the investigation of animal behavior, and the evolutionary origins of human language," they wrote. "Indeed, the evolution of language on Earth may in fact have been driven and constrained by similar principles to those operating on life on other planets."

The researchers have proposed the establishment of a large cross-species database of communicative signals, made available to all SETI and animal behavior researchers.

In addition, they also proposed that tools, algorithms and software used to analyze these signals should be made publicly available for application to these data sets, "so that comparative studies can take full advantage of the expertise from the biological, mathematical, linguistic and astronomical communities."

Complex vocalizations

The topic of dolphin language interpretation, as well as the vocalizations of humpback whales and the field of non-human communications more broadly, is increasingly drawing the interest of SETI researchers and astrobiologists, explained Bill Diamond, president of the SETI Institute.

Humpback whales have very complex vocalizations, Diamond told Space.com, "where it seems clear that they are transmitting information and not simply making sounds associated with mating, feeding or dealing with threats. They plan ahead and communicate complex instructions to one another."

Leading that look is SETI researcher Laurance Doyle, who's working on a project in partnership with the Alaska Whale Foundation to study the vocalizations of humpback whales.

Fundamental rules

For Diamond, the relevant research question is whether or not there are some fundamental mathematical rules associated with the transmission of information that would be universal — like the laws of physics and chemistry — within our known universe.

"If there's an underlying rule structure to the transmission of information, and we can decipher it," Diamond said, "we would firstly be able to recognize a detected SETI signal as containing information, and therefore intelligence. And, possibly, we might even ultimately be able to translate it!"

According to Diamond, "there's definitely a connection between SETI/astrobiology and the study of non-human communication and non-human intelligence."

Scientists from NASA's Jet Propulsion Laboratory (JPL) in Southern California, along with researchers in India and Saudi Arabia, have discovered 26 previously unknown bacterial species in the clean rooms that were used to prep NASA's Phoenix Mars lander for its August 2007 launch.

Clean rooms are decontaminated and intensely controlled environments specifically designed to prevent microbial life from hitching a ride into space. But some microorganisms, known as extremophiles, show impressive resilience in inhospitable environments, whether that's the vacuum of space, hydrothermal vents on the slopes of undersea volcanoes, or even NASA clean rooms.

"Our study aimed to understand the risk of extremophiles being transferred in space missions and to identify which microorganisms might survive the harsh conditions of space," study team member Alexandre Rosado, a researcher at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, said in a statement.

"This effort is pivotal for monitoring the risk of microbial contamination and safeguarding against unintentional colonization of exploring planets," Rosado added.

These hardy microbes may also offer insights that could benefit life on Earth. The scientists performed genetic research on samples gathered from the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center in Florida, one of the last stops for Phoenix before its launch from neighboring Cape Canaveral Space Force Station (then known as Cape Canaveral Air Force Station).

They found 53 strains that they determined belonged to 26 novel species. And they dug into the genomes of these newfound extremophiles, looking for clues that could help explain their extraordinary survivability. The keys might be in genes linked to DNA repair, detoxification of harmful substances and boosted metabolism, according to the team.

"The genes identified in these newly discovered bacterial species could be engineered for applications in medicine, food preservation and other industries," said Junia Schultz, a postdoctoral fellow at KAUST.

And, of course, the research will help NASA improve its clean room protocols to minimize the risk of biological contamination on future missions.

"Together, we are unraveling the mysteries of microbes that withstand the extreme conditions of space — organisms with the potential to revolutionize the life sciences, bioengineering and interplanetary exploration," said Kasthuri Venkateswaran, a retired JPL scientist and a lead author of the study on the research, which was published May 12 in the journal Microbiome.

The image, a blurry composite of more than a thousand grayscale snapshots later colorized by scientists, was taken during a precision flyby of Mars on March 1, 2025. At its closest point, the spacecraft skimmed just 550 miles (884 kilometers) above the Martian surface, in a maneuver known as a gravity assist, which used the Red Planet's gravitational pull to slow the spacecraft and adjust its orbit around the sun ahead of a crucial leg of its nearly 2-billion-mile (3.2 billion km) journey to Jupiter.

The brief encounter also served a scientific purpose: It gave the mission team a chance to test the spacecraft's instruments in deep space, including the thermal imager E-THEMIS (short for Europa Thermal Imaging System), which will eventually scan Europa's surface for signs of recent or ongoing geologic activity. Over an 18-minute span on March 1, the instrument took over 1,000 grayscale images — one per second — which began arriving on Earth on May 5, according to a NASA statement.

To confirm the instrument's accuracy, the mission team compared the new infrared imagery with long-term thermal maps of Mars gathered by NASA's Mars Odyssey orbiter, which has been observing the Red Planet since 2001. The Odyssey team even coordinated observations before, during, and after the Europa Clipper flyby to allow for a direct side-by-side comparison, according to the statement.

"We wanted no surprises in these new images," Phil Christensen, a professor of earth and space exploration at Arizona State University who serves as the principal investigator of the E-THEMIS instrument, said in the statement. "The goal was to capture imagery of a planetary body we know extraordinarily well and make sure the dataset looks exactly the way it should, based on 20 years of instruments documenting Mars."

E-THEMIS detects infrared light — essentially heat — allowing scientists to map temperatures across a planetary surface. After the spacecraft reaches the Jupiter system in 2030, these thermal scans will help identify hotspots that could point to recent geologic activity beneath Europa's icy shell, according to the statement.

Infrared imaging will also help pinpoint where Europa's vast subsurface ocean might lie closest to the surface, scientists say. The moon is etched with ridges and fractures, features that scientists suspect result from oceanic forces — like rising water or convection currents — pulling apart the ice from below.

"We want to measure the temperature of those features," Christensen said. If Europa is active, its fractures could be warmer than surrounding ice — especially where the ocean lies near the surface or past eruptions left lingering heat, he added.

The Mars flyby also marked the first full in-flight test of Clipper's radar instrument, which couldn't be tested in its entirety on Earth due to the size of its antennas. Preliminary telemetry suggests the test was successful, with detailed analysis of the data still to come, the statement read.

With the Mars flyby complete, Clipper's next gravity assist will come from Earth in 2026. The spacecraft is expected to enter Jupiter orbit in April 2030, after which it will begin a series of 49 close encounters with Europa that will allow scientists to investigate the moon's life-hosting potential.

While it's not exactly a social science, it turns out bacteria have their own versions of these social structures, too — and because the earliest fossil evidence for life on our planet was indeed bacterial, studying how bacteria live together may help microbiologists piece together how life began on Earth long ago. One day, it may help us discover life on other planets.

Along these lines, in research published last year, scientists took a closer look at the behavior of a type of bacteria called multicellular magnetotactic bacteria (MMB). What they found was fascinating: MMB has a peculiar way of grouping. Despite each member of this bacterial clan existing as a single-celled organism, none of them can survive that way. Instead, they combine together and act as one giant, multicellular organism that scientists call "consortia."

Another special element of MMB is the "magnetotactic" in its name, which means it orients itself based on Earth's magnetic field. If you compare MMB to a social cell of people, which shifts toward a social ideal, MMB orients itself and knows where to be based on the Earth's magnetic poles.

MMB lands "somewhere in-between a single-celled organism and much more complex life" Roland Hatzenpichler, a microbiologist and associate professor in the Department of Chemistry and Biochemistry at Montana State University, Bozeman and author of the new research, told Space.com. He described the consortia as "anywhere from 30 to 100 cells" living together. The sheer existence of MMB also suggests they may be caught in one of the "bottlenecks" of life formation on Earth, according to Hatzenpichler.

In other words, perhaps MMB is caught in a stage of evolution between a single-celled organism and a more complex, multicellular form of life, like an insect or a fish..

In other words, perhaps MMB was not meant to be a single-celled organism, but just couldn't transition to its multicellular future.

MMB doesn't just want to stay connected — it needs to for survival.

Where is MMB found?

The study researchers got their MMB samples from a tidal pool in Massachusetts, which Hatzenpichler is a known site for purple sulfur bacteria. He described the sediment containing the MMB as brown with purple dots.

"The pond itself is basically just this brownish, gooey sediment," Hatzenpichler said. "Sprinkled in are these purple bacteria."

In terms of all known life on Earth, there's really no other organism that compares to MMB, Hatzenpichler said.

There are different species of MMB, Hatzenpichler said, "but they are all pretty related to each other."

Working together; dying together

Compared to single-celled organisms, which can swim freely using their whip-like tails known as "flagella," MMB have some communicating to do in order to move. Otherwise, there would be a conflict of interest, so to speak.

"If the whole thing moves right, it means that the bacterial cells on one side need to stop spinning, or spin the other direction than the ones on the opposing side," Hatzenpichler said.

He explained that in order to pull this off, there "must be some quick social interaction at the very least to communicate, 'okay, who is swimming forward now and who is not doing that.'"

This type of social cuing between bacteria isn't completely unique, though. Hatzenpichler said a bacterial social cueing phenomenon called "quorum sensing" has been studied for a while, and usually dictates movement or helps bacteria discern how many of their own kind are around them. Disease-causing bacteria, for example, may benefit from sticking together as it makes it harder for the immune system to attack, Hatzenpichler explained.

But what is the purpose of MMB — or of multicellular structures that aren’t exactly multicellular? According to Hatzenpichler, scientists don't exactly know. An obvious con is that if a cell ever wants to live individually again, for whatever reason, they can't.

"It's good to work together, right?" Hatzenpichler said. However: "At some point it might not be beneficial anymore to stick around with your buddies. But if you don't, you die."

But cooperating together may also be advantageous if you're able to split up the work. And, on a much smaller scale, scientists may eventually find that what happens in MMB consortia could mirror the different jobs cells have in the human body.

"Your heart cells do something completely different than your brain cells, which are completely different than the lung and so on," Hatzenpichler said. More studies are needed to see if there is such a "mutually exclusive" relationship with MMB, as has been seen among other organisms that don't have an obligate multicellular lifestyle. (Obligate is the scientific term that means the MMB can’t survive if separated as a single cell.)

"We're not there yet, but I think this is basically where the research is going now," he said.

Life formation and being 'more than the sum of parts'

Perhaps the most beautiful thing about MMB is that it poses philosophical questions as well as scientific ones: Is it multicellular or not, and what does MMB say about life that's more complicated than bacteria?

"You could see this entirety of 50 cells as one organism, so to speak, because individually, they die if they separate — they show unified behavior towards a common goal," Hatzenpichler said.

"I think the same argument can be made for an animal," he said. "Sometimes our cells fight for our overall health, and other times, they don’t."

Another takeaway from the latest research on MMB is what it suggests about life formation in general, and how life can build very complex structures out of something comparatively simple, Hatzenpichler said. In the future, it's possible more research on unique organisms like MMB may even aid discovery of life outside Earth.

"You have this emergent phenomena that comes out of that, where the system is more than the sum of its parts."

The team's research was published on July 11, 2024 in the journal PLOS Biology.

Jake Taylor of the University of Oxford in the U.K., who studies atmospheres of exoplanets, used a basic statistical test to identify telltale signs of gas molecules in the atmosphere of the exoplanet at hand, K2-18b. Taylor did this in such a way that the test didn't assume which gases might be present. Instead of the distinct bumps that typically indicate the presence of detectable gas molecules, Taylor saw the data appearing consistent with a "flat line," according to the new study, which was posted to the preprint archive on April 22 and has yet to be peer reviewed. What this means is the data is likely too noisy — or the signal too weak — to draw definitive conclusions.

"This is evidence of the scientific process at work," Eddie Schwieterman, an assistant professor of astrobiology at the University of California, Riverside, who was not involved with the new research, told Space.com. "That's exactly what we want — multiple, independent groups or individuals to analyze and interpret the same data. This is one, and hopefully more will follow."

Aliens or noise?

In 2023, Nikku Madhusudhan of the University of Cambridge and his colleagues first announced the detection of dimethyl sulfide (DMS) on K2-18b, an exoplanet nearly nine times more massive than Earth located about 120 light-years away in the life-friendly "habitable zone" of its star. This detection was made with an instrument on the James Webb Space Telescope (JWST). Then, on April 17, the same team claimed it used a different JWST instrument and found stronger and clearer evidence for the molecule — and a potentially life-rich ocean world — when compared to the 2023 DMS detection, which was not upheld by independent analyses.

On Earth, DMS is almost exclusively produced by life forms like marine algae, making it a possible "biosignature" in the search for extraterrestrial life. "These are the first hints we are seeing of an alien world that is possibly inhabited," Madhusudhan told reporters in a press briefing. "This is a revolutionary moment."

Although the announcement sparked excitement and made global headlines, scientists not involved with the research quickly cautioned that the results are preliminary and come with several caveats.

Chief among them was the fact that Madhusudhan's team reported the DMS detection with three-sigma significance, indicating a 0.3% chance it could be a fluke — well below the five-sigma standard (0.00003% chance) required for solid scientific discoveries. Critics also raised concerns that the team's data pushes the JWST to its limits, noted the absence of expected molecules like ethane that typically appear alongside DMS, and argued that the researchers may have used a biased model that inflated the significance of the DMS detection.

Taylor's findings, based on a simple model commonly used by astronomers as a "first pass" analysis, add to the skepticism, suggesting the detection's significance was overstated. Yet, Madhusudhan and his team remain undeterred, noting that Taylor's models are too simplistic to capture the complex behavior of atmospheric molecules in the wavelengths their JWST data represent.

"There is nothing in this paper that worries me or seems relevant to the discussion about our result," Madhusudhan said in an email to NPR. "I am only slightly surprised that the bar is so low for a rebuttal!"

To confirm a discovery, results must be supported by independent lines of evidence, show strong statistical significance, and rule out non-biological explanations, astrobiologist Michaela Musilova, who was not involved in either of the new studies, told Space.com. "So far, all data we have been able to review related to K2-18b do not meet these requirements."

Back to square one?

Underlying the debate is the broader question of whether K2-18b is even habitable to begin with.

Recent research suggests the planet may be too close to its star to support liquid water on its surface — placing it outside the habitable zone and contradicting earlier conclusions by Madhusudhan and his team that it could be an ocean world. Moreover, scientists announced they found traces of DMS on a cold, lifeless comet in 2024, raising the possibility that such molecules could form through as-yet unknown chemical processes, Musilova noted.

Musilova, Schwieterman and other experts agree additional independent analyses are necessary to determine whether the signals found by Madhusudhan and his team truly represent DMS or DMDS in K2-18b's atmosphere, or are simply the artifact of noise in the data. The signals might be absent, or they could be present but currently undetectable. Either way, more observations are needed to resolve the uncertainty, said Schwieterman.

"If the ultimate result of this story is that the public is more circumspect about future claims of life detection, that's not a terrible thing," he said.

Darryl Z. Seligman is a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow/Assistant Professor of Physics and Astronomy at Michigan State University.

Scientists owe it to the general public to convey their results accurately and honestly.

Over the last week, I — along with most of my astronomer and planetary scientist colleagues — received emails, texts, and phone calls from family, friends, and the media. Everyone was asking the same question: "Did we really find evidence of life on a planet outside of our own solar system?" This outpouring of communication was prompted by a recent article published by The New York Times entitled "Astronomers Detect a Possible Signature of Life on a Distant Planet."

The Astrophysical Journal Letters recently published an article entitled "New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI." The peer-reviewed article reported a detection — albeit at low statistical significance — of the presence of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS). DMS and DMDS can be produced both by living organisms (such as phytoplankton) or from run-of-the-mill chemical reactions that are not associated with life at all. However, the authors issued a press release only focused on aliens.

If this news article was a wildfire spreading out of control, then every astronomer was a firefighter, desperately trying to minimize the damage spurred by the press release accompanying the paper. Why? Because the news article was exaggerated.

Related: Did we actually find signs of alien life on K2-18b? 'We should expect some false alarms, and this may be one'

This tale is not new to astronomers. In fact, it has played out over and over again: fossilized microbes were found on Mars (nope), an interstellar interloper was an alien spaceship (nope), and bacterial life exists in the clouds of Venus (to be tested), to name a few of our own wolves.

As a collective, we can't resist anthropomorphizing the natural world. Many cultures thought there was a man in the moon, until we learned that his face was a series of craters. In 1976, the Viking 1 orbiter took a photo of a face on Mars, which turned out to be an optical illusion of shadows on a hill. These claims highlight the delicate balance between philosophy and science. In philosophy, we can conceptually explore our existence and place in the universe. In science, we need hard evidence.

Since its foundation, NASA has been a constant source of support for the development and the launch of observatories designed to figure out if we are alone in the universe. We want to understand if terrestrial planets orbiting other distant stars could harbor life. In December 2021, NASA launched the James Webb Space Telescope (JWST), which is dedicating hundreds of hours to observing these planets to determine whether or not they have atmospheres.

We want to understand if Jupiter's moon Europa has a liquid ocean with more water than all of Earth's oceans combined hidden below its icy surface. In October 2024, NASA launched Europa Clipper, which will determine the thickness of this outer icy layer and characterize the Galilean moon's overall geology.

We want to understand if Saturn's moon Titan has the proper composition to support prebiotic chemistry. In April 2024, NASA approved the Dragonfly mission, a car-sized nuclear-powered drone, to fly over and land on Titan with an estimated 2028 launch. Dragonfly will measure the composition of Titan up close and search for chemical signatures that could indicate the presence of life.

All of these great observatories will help us to understand fundamental truths about celestial bodies. But if we want to answer one of humanity's oldest questions — are we alone? — then we have to be able to communicate our results. Our ability to trust real scientific discoveries is crumbling under the weight of those who want to be "the first," undermining the efforts of thousands of scientists and engineers pursuing truths with due diligence and following the rules of the scientific method we learned in elementary school. When people believe that we have found life on other planets when we have not, we've lost more than public trust — we've lost our own direction.

Flying to Europa or Titan, and looking at the atmospheres of distant exoplanets, are no longer the subject of fantastical science fiction stories. These aren't dreams. This is all of our present-day reality, and even some of our day jobs. When we sit at our desks and analyze data from these observatories, we are inching toward the answer we want so badly. But over-sensationalizing at best — and even outright lying at worst — about the results of these observatories erodes public trust and ultimately harms the very institutions working in the pursuit of scientific discovery.

This comes at a critical time, when the White House has proposed to slash NASA's science budget by nearly 50% and the National Science Foundation's (NSF) budget by up to 50%. Cutting these programs isn't just shortsighted — it's self-destructive. NASA and NSF fund science across all disciplines. Both agencies have long led and participated in global efforts to pursue scientific breakthroughs, like JWST.

Related: The search for alien life

With these proposed budget cuts, we risk losing the scientists and engineers whose research is the foundation for future mission development.

We risk losing the ability to support and train the next generation of scientists.

We risk missing the very voices that could guide us through our most profound discoveries.

We risk losing touch with our fundamental nature to ask and answer questions about our place in the universe.

The search for life beyond Earth has been an ongoing endeavor since the first philosopher questioned if we are alone in the universe. It relies on our ability to connect astronomy, biology, chemistry, physics, engineering, and even philosophy, which initially paved the way for scientific thinking. From all of these angles, we will continue to pursue an answer to this age-old question.

Yet, in our endeavor, we must remember that our mission is greater than the research of the individual. We must not stoop to using over-sensationalized results to support our own personal agendas. And, we must not forget our collective direction: the pursuit of truths and our responsibility to share these truths — and only these truths — with humanity.

Dragonfly, a car-sized, nuclear-powered rotorcraft designed to investigate Titan's potential to host life, passed its Critical Design Review, NASA announced on Thursday (April 24).

"Passing this mission milestone means that Dragonfly's mission design, fabrication, integration and test plans are all approved, and the mission can now turn its attention to the construction of the spacecraft itself," a NASA statement reads.

The $3.35 billion Dragonfly mission was first selected by NASA in 2019 and is being designed and built under the direction of the Johns Hopkins Applied Physics Laboratory (APL) in Maryland, with APL's Elizabeth Turtle as the principal investigator.

The mission has been hit by delays and cost overruns, but studying Titan is considered a high priority by scientists for its potential to harbor alien life.

The mission is set to launch no earlier than July 2028 on a SpaceX Falcon Heavy rocket from NASA's Kennedy Space Center in Florida. The spacecraft will then embark on an almost seven-year-long voyage through deep space to the Saturn system, with the goal of spending more than three years studying areas across Titan's frigid and diverse surface.

Equipped with cameras, sensors and samplers, Dragonfly will assess Titan's habitability, looking out for prebiotic chemistry as well as potential signs of life.

Related: NASA greenlights 2028 launch for epic Dragonfly mission to Saturn's huge moon Titan

Titan is Saturn's largest moon, and the second largest in the solar system behind Ganymede of Jupiter. Its thick, hazy atmosphere shrouds a surface featuring dunes of hydrocarbons and methane lakes. Beneath the moon's icy crust, scientists think there's a subsurface ocean of salty water, adding to the possibilities for Titan to harbor life.

In 2005, NASA's Cassini mission delivered the Huygens probe to Titan. The European Space Agency-built Huygens made a parachute-assisted landing, which provided profound insights into the giant moon. Dragonfly, if successful, could revolutionize our understanding of how life might arise elsewhere in the solar system.

The Extant Life Volumetric Imaging System, or ELVIS, was sponsored by the ISS National Laboratory and developed by researchers at Portland State University (PSU), in partnership with NASA's Jet Propulsion Laboratory in Southern California.

The instrument arrived at the orbiting lab this morning (April 22) on a SpaceX Dragon cargo capsule, which is flying the company's 32nd Commercial Resupply Services mission for NASA.

ELVIS uses cutting-edge holographic technology known as volumetric imaging to create 3D images of microbes and other cells. The mission aims to study how microscopic life adapts to the harsh environment of space; its results could eventually help scientists identify life on other planets and moons, such as Jupiter's Europa and Saturn's Enceladus, team members say.

Related: The search for alien life

Unlike traditional two-dimensional microscopes, ELVIS allows researchers to observe the intricate structure and behavior of living cells in a volumetric format. The system enables detailed biological assessments of how cells change in microgravity — a condition only consistently available to researchers aboard the ISS.

"We are thrilled to leverage the ISS National Lab to prepare ELVIS for its future roles in space exploration missions,” Jay Nadeau, a PSU physics professor and principal investigator on the project, said in a PSU statement.

"The successful operation of ELVIS in the demanding conditions of space not only paves the way for its use in off-Earth environments but also holds implications for enhancing biomedical and microbiological research on our planet," Nadeau added.

Nadeau first proposed using holographic microscopy as a life-hunting technique back in 2017, in a paper arguing that it could potentially detect minute signs of life that regular 2D microscopes might miss.

"It's harder to distinguish between a microbe and a speck of dust than you'd think," Nadeau said in 2017, when she was a research professor of medical engineering and aerospace at the California Institute of Technology in Pasadena.

"Digital holographic microscopy allows you to see and track even the tiniest of motions," she went on to say.

This capability not only allows for possibly identifying microbes among inert matter, as Nadeau and her colleagues proposed in that 2017 paper, but also enables tracking cellular changes that might not be apparent from flat, 2D imaging. ELVIS therefore could see changes induced in a cell's structure in the extreme conditions of space better than a 2D image could.

During its ISS mission, ELVIS will study two Earth-based organisms known for their toughness and resilience: Euglena gracilis, a highly adaptable microalga, and Colwellia psychrerythraea, a cold-loving bacterium found in deep ocean waters. By analyzing these lifeforms in microgravity, scientists aim to uncover both observable and genetic changes that could help life persist in alien environments.

Engineered for space conditions, ELVIS includes durable, low-maintenance components and automation features that reduce the need for astronaut intervention, allowing experiments to run with minimal disruption, mission team members said.

On Earth, large rivers create deltas with sediment-filled wetlands. Deltas form when the mouth of a river empties into another body of water. Besides Earth, Titan is the only planetary body in our solar system with liquid flowing on the surface.

Researchers recently looked for deltas on the big Saturn satellite but came up empty.

"We take it for granted that if you have rivers and sediments, you get deltas," study leader Sam Birch, an assistant professor in the Department of Earth, Environmental and Planetary Sciences at Brown University in Rhode Island, said in a statement.

"But Titan is weird. It's a playground for studying processes we thought we understood," he added.

Related: Titan: Facts about Saturn's largest moon

The researchers were hoping to find deltas on Titan, because these landforms feature lots of sediment. The sediment in deltas tends to come from a large area, and deltas gather it in one place. Studying such sediment could reveal insights about Titan's climate and tectonic histories — and perhaps even possible signs of alien life.

"It's kind of disappointing as a geomorphologist, because deltas should preserve so much of Titan's history," Birch said.

We know that Titan's surface has flowing liquid methane, because NASA's Cassini spacecraft spotted evidence of the stuff on multiple flybys. Cassini used synthetic aperture radar (SAR) to look through Titan's thick atmosphere during these close encounters and found channels and large flat areas that are consistent with large bodies of liquid.

But shallow liquid methane is largely transparent in Cassini's SAR data. Scientists have therefore had a hard time studying Titan's coastal features, because it's hard to make out where the coast ends and the sea floor starts.

So, Birch's team came up with a computer model that simulates what Cassini's SAR would see when looking at Earth. But the model replaced the water in Earth's rivers and oceans with Titan's liquid methane.

"We basically made synthetic SAR images of Earth that assume properties of Titan's liquid instead of Earth's," Birch said. "Once we see SAR images of a landscape we know very well, we can go back to Titan and understand a bit better what we're looking at."

The synthetic SAR images of Earth that they created "resolved large deltas and many other large coastal landscapes," according to the researchers.

They say that new analysis of the Cassini SAR data also revealed other mysteries. For example, Titan's coasts appear to have pits of unknown origin deep within lakes and seas, and deep channels cut across the moon's sea floors offer no clue to how they got there.

"This is really not what we expected," Birch said. "But Titan does this to us a lot. I think that's what makes it such an engaging place to study."

The new study was published in the Journal of Geophysical Research: Planets on March 25.

The team's findings, based on their analysis of James Webb Space Telescope (JWST) data, point to an abundance of dimethyl sulfide (DMS) molecules in the atmosphere of a planet known as K2-18b, which circles its star about 120 light-years from Earth in the Leo constellation. Because DMS is almost exclusively produced by life forms like marine algae on Earth, astronomers consider it a potential "biosignature" in the search for life — past or present — elsewhere in the universe. According to Nikku Madhusudhan of the University of Cambridge and his colleagues, the best explanation for the presence of these molecules — DMS and its chemical cousin dimethyl disulfide, or DMDS, which is also a potential biosignature — on K2-18b is therefore that the planet could be an ocean world "teeming with life."

"These are the first hints we are seeing of an alien world that is possibly inhabited," Madhusudhan told reporters in a press briefing. "This is a revolutionary moment."

However, the excitement sparked by the announcement was quickly tempered by a wave of caution, with scientists emphasizing that the results are still preliminary and come with several caveats. Chief among them is the fact that Madhusudhan and his team reported their DMS detection with a three-sigma statistical significance, indicating a 0.3% chance of it being due to random chance. Experts point out that this falls short of the typical five-sigma standard required for a scientific discovery to minimize false positives, which translates to a 0.00003% chance that the findings are due to a statistical fluke.

Additionally, the data gathered for the new K2-18b study seems to push the JWST to its limits, and critics say the researchers might have used a biased model that effectively artificially inflated the significance of DMS wafting in the planet's atmosphere.

"Concluding that DMS has been detected appears to be premature," Manasvi Lingam, an astrobiologist at the Florida Institute of Technology, who wasn’t involved in the new research, told Space.com. The latest research "involves new data, but until that data has been analyzed independently by others, we cannot make any claims about K2-18b's habitability and the possible existence of life."

Eddie Schwieterman, an assistant professor of astrobiology at the University of California, Riverside, who was not involved with the new research, said he was particularly surprised that ethane wasn't found alongside the possible DMS or DMDS signal. The host star's UV radiation should break down the molecules and form abundant ethane as a byproduct, he explained, meaning its absence in Madhusudhan's data doesn't align with scientists' understanding of planetary atmospheres.

"Either our models are in error, or the DMS/DMDS might not exist," Schwieterman told Space.com. "Finding life outside the solar system won't be a 'one and done' detection — along the way, we should expect some false alarms and this may be one."

Fresh eyes on old data

Madhusudhan and his colleagues first reported a possible DMS detection on K2-18b in 2023, using the JWST then as well. That finding met its own share of skepticism, and was not upheld by independent analyses of the same data. However, this latest study utilized a different JWST instrument and analyzed the planet at different wavelengths, which the research team claims provides a stronger and clearer indication of DMS/DMDS molecules.

Still, many scientists are once again injecting doses of skepticism on the high-profile claim, emphasizing the need for rigorous scientific scrutiny because there is potential for more ordinary, non-biological explanations for the sought-after molecule in K2-18b's atmosphere.

Christopher Glein, a planetary scientist at the Southwest Research Institute in Texas who was not involved with the new study, said his reaction to the announcement "is one of interest but restraint."

"We need to resist the temptation to find a smoking gun," he told Space.com. "The search for life is hard. For a convincing case to be made, multiple self-consistent lines of evidence will need to be assembled."

Other critics argue Madhusudhan and his team engaged in "statistical hacking" by building a selective model where DMS and DMDS are the only explanations for half of K2-18b's atmospheric light spectrum, thereby artificially boosting the molecules' significance.

"Reproducibility is a hallmark of science. We need to see that moving forward," said Glein. "Did they find a needle in the haystack, or just a sharp piece of hay?"

Echoes of life or lifeless chemistry?

Before a planet can be inhabited, it must be habitable.

In 2021, K2-18b's initial atmospheric composition had led Madhusudhan and his colleagues to suggest the planet harbors a warm ocean blanketed by a hydrogen-rich atmosphere. Key to that conclusion was the detection of carbon dioxide, or CO2, in the planet's atmosphere, which led the team to suggest the world is potentially capable of hosting microbial life.

However, more recent studies have questioned that CO2 calculation, raising the possibility that the planet may be too close to its star to support stable liquid water on its surface.

"As much as we want it to be, I am not sure that K2-18b is habitable," said Glein.

Scientists are also at a very early stage in understanding the chemistry of sub-Neptune exoplanets like K2-18b, he said, which means we aren't so sure yet what the abiotic background, or non-biological composition, of these worlds should look like. "These things take time — we've learned in recent years that an anomaly does not necessarily mean life," said Glein.

Matt Genge, a planetary scientist at the Imperial College London, who was not part of the new research, noted that more context and possible formation pathways are needed to explain the abundance of detected molecules in the planet's atmosphere before scientists can confidently attribute the signal to life rather than non-living chemistry or geology.

"When a discovery is as monumental as the discovery of alien life, the bar is set very high for convincing evidence," said Genge. "As a geologist who studies planets, I question the assumption that these molecules can only be produced by life."

If future observations determine that DMS or DMDS is indeed present in the planet's atmosphere, "then it's possible we might be seeing evidence of some cool chemistry rather than biochemistry," said Glein. "As Carl Sagan used to say, life is the hypothesis of last resort."

There is also disagreement about whether DMS should even be considered a reliable biosignature, astrobiologist Michaela Musilova, who was also not involved in the new research, told Space.com. A recent study suggested atmospheric interactions between UV radiation, methane and hydrogen sulfide could lead to a buildup of DMS and DMDS in the upper atmosphere of an otherwise inhospitable world.

Traces of DMS have also been detected on a cold comet devoid of life, which "suggests that these types of molecules could be produced by chemical processes that we are not yet familiar with," said Musilova.

"Until findings are confirmed by multiple teams and through multiple methods, everything directly related to biosignatures and detecting alien life remains, for me, in the 'potential discovery' category," she added.

The search for extraterrestrial life is sprinkled with tantalizing hints that have often ultimately turned out to have non-biological explanations. For instance, a potential signal of phosphine — also considered a possible biosignature — in the clouds of Venus ended up being a false alarm. The complexity of exoplanetary atmospheres and the limitations of current observational technology mean that interpreting signals from light-years away is a delicate and challenging process.

Even if K2-18b doesn't ultimately prove to host life, the techniques and insights gained from studying it will be useful for future investigations of other potentially habitable worlds, said Musilova. "Every new set of data in the astrobiology field is valuable and it can help us advance towards better understanding whether alien life exists elsewhere in the universe and how our life came to be on Earth."

"I just want to make sure that we balance our enthusiasm with a proper dose of patience," said Glein. "It's going to be a fun ride, but we should fasten our seatbelts."

In 2023, researchers using NASA's James Webb Space Telescope (JWST) reported the potential presence of dimethyl sulfide (DMS) on K2-18b, which is nearly nine times more massive than Earth and circles in the "habitable zone" of a star about 120 light-years away from us.

Here on Earth, DMS is produced primarily by life — most prolifically by phytoplankton and other marine microbes — so the 2023 study was met with some enthusiasm. The excitement was tempered, however, by the preliminary nature of the find; JWST's observations were consistent with the presence of DMS but did not confirm it. So the study team looked again, but in a slightly different way this time.

JWST can probe exoplanet atmospheres when these worlds "transit," or cross the face of, their host stars from the observatory's perspective: The telescope detects certain molecules in the air based on the wavelengths of starlight that they absorb.

Related: Does exoplanet K2-18b host alien life or not? Here's why the debate continues

The team made the original, tentative DMS detection using JWST's NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) instruments. For the new study, the researchers employed the $10 billion telescope's Mid-Infrared Instrument (MIRI), which scrutinizes different wavelengths of light.

MIRI also detected the fingerprint of DMS (and/or dimethyl disulfide, or DMDS, a close chemical cousin and also a potential biosignature), the researchers report in the new study, which was published online today (April 17) in The Astrophysical Journal Letters.

"This is an independent line of evidence, using a different instrument than we did before and a different wavelength range of light, where there is no overlap with the previous observations," Nikku Madhusudhan, a professor at Cambridge University's Institute of Astronomy, who led both K2-18b studies, said in a statement today. "The signal came through strong and clear."

Based on its size and other characteristics, astronomers suspect that K2-18b may be a "Hycean" world — a class of exoplanet proposed in 2021 that has a huge liquid-water ocean and a hydrogen-rich atmosphere. ("Hycean" is a portmanteau of "hydrogen" and "ocean.")

And K2-18b's air is also rich in DMS and/or DMDS, according to the new study. The researchers estimate concentrations of more than 10 parts per million by volume, compared to less than one part per billion for them here on Earth.

"Earlier theoretical work had predicted that high levels of sulfur-based gases like DMS and DMDS are possible on Hycean worlds," Madhusudhan said. "And now we’ve observed it, in line with what was predicted. Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have."

Madhusudhan and his team aren't claiming to have detected alien life; they say that more research is needed to confirm and extend their findings. Other scientists feel the same way — and some are injecting heavier doses of skepticism into the debate around K2-18b and its life-hosting potential.

One of them is astronomer Chris Lintott, who took issue with Madhusudhan's "strong and clear" characterization of the DMS/DMDS signal.

"Meanwhile, the peer-reviewed paper says 'While [the presence of molecules] DMDS and DMS best explains the current observations, their combined significance … is at the lower end of robustness required for scientific evidence," Lintott, an astrophysics professor at the University of Oxford, wrote on the social media site BlueSky yesterday (April 16).

Detecting signs of alien life is a tricky business, and confirming them is even tougher — especially on a world like K2-18b, which we won't be able to investigate up close for the foreseeable future, if ever. So we should expect the debate, and the data collection, to continue.

A new study backs up that idea — but with a twist. Yes, alien life could be there, researchers say, but probably not in the abundance we once hoped.

"We focus on what makes Titan unique when compared to other icy moons: its plentiful organic content," study co-lead author Antonin Affholder, a postdoctoral research associate in the University of Arizona's Department of Ecology and Evolutionary Biology, said in a statement. "There has been this sense that because Titan has such abundant organics, there is no shortage of food sources that could sustain life."

NASA's Cassini mission flew past Titan over 100 times, and in 2005, the European ride-along probe Huygens landed on its surface. On its way down, Huygens collected valuable data on Titan's dense atmosphere, finding a host of photochemical reactions — light-driven chemical reactions that shape the moon's chemical environment and could play a role in making it potentially habitable. This is because such reactions can create complex organic molecules, including some that could be the building blocks for life.

Related: Titan: Facts about Saturn's largest moon

The idea is that these organic molecules eventually settle on Titan's surface and, through a mix of material exchange and possible geochemical processes, find their way down into the moon's hidden ocean — potentially making the dark waters below a habitable environment.

But "potentially" is a key word here, according to the new study.

"We point out that not all of these organic molecules may constitute food sources, the ocean is really big, and there's limited exchange between the ocean and the surface, where all those organics are, so we argue for a more nuanced approach," said Affholder.

Using bioenergetic modeling — a method that uses mathematical simulations to quantify the energy needed to make and break chemical bonds in a biological system — the team attempted to identify a plausible scenario in which life could emerge on Titan. They landed on a simple and familiar process: fermentation.

"Fermentation probably evolved early in the history of Earth's life and does not require us to open any door into unknown or speculative mechanisms that may or may not have happened on Titan," Affholder said.

Fermentation is a simple metabolic process in which microorganisms, such as bacteria, break down organic molecules like sugars or carbohydrates into simpler compounds. The key part? It all happens without oxygen, which makes it especially relevant for a world like Titan, where oxygen is scarce or absent.

"We asked, could similar microbes exist on Titan?" Affholder said. "If so, what potential does Titan's subsurface ocean have for a biosphere feeding off of the seemingly vast inventory of abiotic organic molecules synthesized in Titan's atmosphere, accumulating at its surface and present in the core?"

Using the simplest of all known amino acids — glycine, which is relatively abundant throughout the solar system — the team's simulations found that conditions on Titan could, in theory, support microbial life through fermentation. However, only a tiny portion of Titan's organic material might actually reach the ocean, depending on how much glycine makes its way down from the surface.

"This supply may only be sufficient to sustain a very small population of microbes weighing a total of only a few kilograms at most — equivalent to the mass of a small dog," Affholder said.

"Such a tiny biosphere would average less than one cell per liter of water over Titan's entire vast ocean," he added. "We conclude that Titan's uniquely rich organic inventory may not in fact be available to play the role in the moon's habitability to the extent one might intuitively think."

That means that, if life does exist on Titan, it could be extremely sparse, making it especially challenging for future missions to detect — like trying to find a needle in a haystack, the team concludes.

The new study was published April 7 in The Planetary Science Journal.

"A simple positive detection would change everything," said astronomer Daniel Angerhausen of ETH Zurich in Switzerland in a statement. "But even if we don't detect life, we'll quantify how rare – or common – planets with detectable biosignatures really might be."

LIFE, the Large Interferometer For Exoplanets, is a proposal for an ambitious new mission designed to reveal how many Earth-like planets out there are inhabited by some form of life. Here's the plan.

Led by ETH Zurich astronomers, the mission concept proposes for four space telescopes to fly in formation around a central "combiner" spacecraft. The idea is that the four space telescopes would fly tens to hundreds of meters apart and collectively act as an interferometer, meaning they'd combine their light detections by feeding signals to the central combiner spacecraft. Furthermore, to block out the glare of a star so that LIFE could detect orbiting exoplanets, the telescopes will employ a technique known as "nulling interferometry," whereby the light of the star is combined "out of phase." This would allow what's known as "destructive interference" to cancel out that light, leaving behind just the light given off by orbiting planets.

LIFE won't be able to directly image exoplanets, but by observing in the mid-infrared it will be able to spectroscopically measure their light and reveal which molecules are present in their atmospheres (if they have one).

LIFE will target dozens of Earth-size planets in the habitable zone of their stars, in the hopes of finding biosignatures, which are atmospheric gases produced, or kept in balance, by life. The likes of oxygen and water vapor are the most obvious of such biosignatures, but others include ozone, methane, nitrous oxide, dimethyl sulphide and phosphine, to name a few.

Currently, however, LIFE is just a concept. It has not yet been adopted by a space agency.

Still, Angerhausen and colleagues at ETH Zurich wanted to find out how much LIFE could tell us, even if it failed to find biosignatures. What would a negative or null result imply about the frequency of inhabited planets in the galaxy? For this, they turned to statistics.

So before we go any further, we also need to delve into the world of statistics to understand their conclusions.

The team employed a Bayesian statistical model to find the smallest number of exoplanets LIFE would need to observe to yield a firm answer as to how common inhabited worlds are. Bayesian statistics has to do with finding the probability of an outcome based on other probabilities that we already know (these are described as "priors"). Bayesian statistics describes the level of confidence or belief we have that an event will occur based on what we know about a certain situation.

For a mundane example, suppose you hear a loud bang. Was it thunder? Maybe a firework? Bayesian statistics allows you to deduce the answer based on the probabilities of the priors, such as knowing whether fireworks are usually set off around certain times of the year (like New Year's Eve, the fourth July in the United States and Bonfire Night in the U.K.) or if the weather has been forecast to be stormy. Based on these priors, Bayesian statistics allows you to quantify your belief as to whether it was thunder or a firework.

In contrast to Bayesian statistics, an alternative way of looking at probabilities is "frequentist statistics." As the name implies, this describes the probability of an outcome based on the frequency of that event occurring after many trials.

Unlike Bayesian statistics, frequentist statistics does not concern itself with priors. When tossing a coin, frequentist statistics doesn't worry about whether the previous four tosses have all landed on heads. Assuming an unbiased coin, the chances of it landing on heads or tails is always 50%, and over a high enough number of trials this 50% probability would appear readily apparent in the data.

So, back to the question: how many planets could LIFE observe and not find any biosignatures before astronomers can start drawing conclusions regarding the prevalence of life in the galaxy? Through the use of Bayesian statistics, Angerhausen's team found that between just 40 and 80 exoplanets would need to be observed with no detectable biosignatures to conclude with confidence that fewer than 10 to 20% of similar planets in the universe has life. Surveying this many exoplanets is well within LIFE's planned abilities.

If LIFE detects no biosignatures on its sample of planets, it cannot conclude that there is no life anywhere, but it can place a maximum limit on how many planets in the galaxy do have life. And, as the sample size increases, if there continues to be no detection, then that maximum number would decrease further. In other words, LIFE could tell us whether inhabited planets are rare or not.

There will be uncertainties, however. Perhaps a biosignature will be missed — after all, some of these gases are not easy to detect. Or perhaps some planets will be mistakenly included in the sample of potentially habitable planets when, in fact, they do not fit the requirements to be considered potentially habitable in the first place. Again, this could occur because observations are difficult.

"It's not just about how many planets we observe, it's about asking the right questions and how confident we can be in seeing or not seeing what we’re searching for," said Angerhausen. "If we're not careful and are overconfident in our abilities to identify life, even a large survey could lead to misleading results."

To test their conclusion, Angerhausen and colleagues also applied frequentist statistics to the problem. They found the results to be similar.

"Slight variations in a survey's scientific goals may require different statistical methods to provide a reliable and precise answer," said Emily Garvin, a Ph.D. student at ETH Zurich. "We wanted to show how distinct approaches provide a complementary understanding of the same dataset, and in this way present a roadmap for adopting different frameworks."

With luck, if the LIFE mission or something similar ever goes ahead, it will find a planet, or planets, with life of some variety. But even if it doesn't, the results could still be profound and take us one giant leap closer to understanding our place in the universe.

The study was published on April 7 in The Astronomical Journal.

Those potential signs of life are a group of chemicals called methyl halides, which on Earth are produced by some bacteria and ocean algae.

"Unlike an Earth-like planet, where atmospheric noise and telescope limitations make it difficult to detect biosignatures, hycean planets offer a much clearer signal," said Eddie Schwieterman, who is an astrobiologist at the University of California, Riverside, in a statement.

For now, the existence of hycean planets remains hypothetical. Their name is a portmanteau of "hydrogen" and "ocean," first coined in 2021 by planetary scientist Nikku Madhusudhan of the University of Cambridge.

Related: 'Hycean' exoplanets may not be able to support life after all

Hycean planets are expected to orbit red dwarf stars, and the best candidate for a hycean world is the planet K2-18b. This exoplanet, which is categorized as a "sub-Neptune" world, orbits in the habitable zone of a red dwarf star 124 light-years from Earth in the constellation of Leo, the Lion.

The Hubble Space Telescope discovered water vapor in K2-18b's atmosphere in 2019, and JWST has detected the presence of carbon dioxide and methane in the planet's atmosphere, along with a lack of carbon monoxide and ammonia — exactly as predicted by the hycean planet hypothesis. There's also tentative evidence that a compound called dimethyl sulfide, which on Earth is only produced by ocean plankton, also exists in K2-18b's atmosphere, but this evidence continues to prove contentious.

Now a team of researchers at the University of California, Riverside and ETH Zurich in Switzerland have gone a step further. They propose that another family of compounds called methyl halides, generated by microbial ocean life on Earth, could produce a biosignature — that is, a chemical signature of biological life — in the atmosphere of a hycean world that's more easily detectable than the signature of oxygen is on an Earth-like planet.

"Oxygen is currently difficult or impossible to detect on an Earth-like planet," said Michaela Leung of the University of California, Riverside, the first author of a new paper describing the research. "However, methyl halides on hycean worlds offer a unique opportunity for detection with existing technology."

Methyl halides are molecules that incorporate carbon atoms and three hydrogen atoms attached to a halogen atom such as bromine, chlorine or fluorine. (Halogens are group of reactive, non-metallic elements.) On Earth, methyl halides are produced by life, but they are far from abundant in our planet's atmosphere.

On hycean worlds, however, things could be different. Leung's team suspect that the conditions on such worlds, should they exist, would allow methyl halides to accumulate in large quantities in the atmosphere. Furthermore, methyl halides would have strong absorption features in infrared light, at the same wavelengths that the JWST is designed to observe.

"One of the great benefits of looking for methyl halides is, you could potentially find them in as few as 13 hours with James Webb. That is similar or lower, by a lot, to how much telescope time you'd need to find gases like oxygen or methane," said Leung. "Less time with the telescope means it's less expensive."

Related: The search for alien life

There are two caveats to what Leung's team propose. One is that we don't yet know whether hycean worlds actually exist. They were proposed as a possibility to explain certain properties of some warm sub-Neptune-type planets that have average densities that imply a thick hydrogen atmosphere and a deep ocean of liquid water. However, directly observing an ocean beneath such a world's hydrogen envelope is not currently feasible.

The second issue is that we don't know if such oceans could be habitable. A hycean world would be hot, and although the extreme conditions beneath the hydrogen envelope would prevent the ocean from evaporating, it is uncertain whether it would be too hot for life as we know it. However, a positive detection of methyl halides in the atmosphere of a candidate hycean world would be a strong indication that life could exist there in a deep ocean.

If life does exist on such a world, it would have to breathe hydrogen, not oxygen.

"These microbes, if we found them, would be anaerobic," said Schwieterman. "They'd be adapted to a very different type of environment, and we can't really conceive of what that looks like, except to say that these gases are a plausible output from their metabolism."

Anaerobic life — i.e., lifeforms making do without oxygen — exist on Earth, so it wouldn't be truly alien to life on our planet, even if the environment that it would live in is. Earth-like worlds orbiting red dwarfs could be in short supply, since red dwarfs are fierce little beasts, prone to unleashing bursts of harsh radiation that can strip away the atmosphere of an Earth-like planet. However, hycean worlds protected by their thick hydrogen atmospheres might be less vulnerable to attack from their star.

It could therefore be that hycean worlds are where life resides in red dwarf systems, and since red dwarfs make up about three-quarters of all stars in our Milky Way galaxy, there could be many more habitable hycean worlds in the cosmos than Earth-like worlds.

The research by Leung's team was published on March 11 in The Astrophysical Journal Letters.

As some of the most energetic phenomena in the universe, supernovae occurring within 60 light-years of Earth could have stripped our planet's atmosphere of its protective ozone layer, exposing life to damaging ultraviolet radiation from the sun, a team of astronomers has discovered.

"A slightly more distant supernova could still cause considerable loss of life, but at this distance, it would be terrifying," study co-author Nick Wright, an astrophysics professor at Keele University in England, told Space.com via email.

Wright and his team used data on the locations of stars collected by the now-retired Gaia satellite to conduct a virtual census of more than 24,000 of the most luminous stars in the universe. They focused on those located within 3,260 light-years of the sun to identify new groups of young, massive stars and reconstruct nearby star formation history.

"It was only once we had completed the work that we realized we could also use the sample to estimate the supernova rate," said Wright. "When we’d done that, we realized it was very close to the rate of unexplained mass extinction events on Earth!"

Supernovas alligning with extinction events

Wright and his team found the timing of supernovae near Earth aligned with two significant mass extinction events on our planet: the late Devonian, a series of mass extinction events that occurred 372 million years ago, and the Ordovician, which occurred 445 million years ago and was the first of the big five mass extinction events in our planet's history.

75% of all species, particularly in the types of fish found in ancient seas and lakes, while the Ordovician event wiped out about 85% of marine species.

"It surprised me that the two rates were so similar, which made us want to highlight it," said Wright.

Previous research has found evidence of an influx of the radioactive isotope iron-60 in cosmic dust collected from the Antarctic snow and from the surface of the moon, which can only be attributed to interstellar sources like supernovae. Various studies have linked this flux to the depletion of Earth's ozone layer, caused by cosmic rays showered onto our planet by the stars' explosive deaths.

"Supernovae produce a very high flux of high-energy radiation, which when it reaches the Earth could cause considerable destruction, including breaking apart the ozone molecules that make up the ozone layer," Wright told Space.com.

This ozone depletion, in turn, is thought to have contributed to at least one widespread extinction of marine mammals, seabirds, turtles, and sharks that occurred around 2.6 million years ago. The primary cause behind the Devonian and Ordovician mass extinction events is not fully understood, but both of them have also been linked to the depletion of Earth's ozone layer.

The new study's simulations showed roughly one to two supernovae occur each century in galaxies like the Milky Way.

Within 60 light-years of Earth — the typical distance at which a supernova could potentially cause catastrophic destruction to life on Earth — the rate of supernovae was 2 to 2.5 per billion years. This estimate is in good agreement with the number of unexplained mass extinction events on Earth — specifically, the Devonian and Ordovician extinctions, both of which occurred within the last billion years — raising the possibility that nearby supernovae may have contributed to these events, according to the study.

"It’s worth noting that we don’t have proof that those extinctions were definitely caused by supernovae, only that the rates match up, and therefore, it seems very plausible," Wright said.

These findings are "a great illustration for how massive stars can act as both creators and destructors of life," Alexis Quintana of the University of Alicante in Spain, who led the new study, said in a statement.

"Supernova explosions bring heavy chemical elements into the interstellar medium, which are then used to form new stars and planets," she said. "But if a planet, including the Earth, is located too close to this kind of event, this can have devastating effects."

The team's research was published on Tuesday (March 18) in the journal Monthly Notices of the Royal Astronomical Society.

That's the conclusion of Florida Institute of Technology researcher Caldon Whyte, who's particularly fascinated by these stellar remnants. Until now, scientists have generally thought that planets orbiting white dwarfs would be unsuitable for life because the dynamic temperature decrease of their dead parent star makes their atmospheres too unstable.

As the James Webb Space Telescope (JWST) increasingly investigates white dwarf systems, however, Whyte and colleagues developed a model capable of assessing if two key life-sustaining processes could occur in the range of orbits around a white dwarf temperate enough to allow liquid water to exist. This region around stars is referred to as the habitable zone or Goldilocks zone, because it's neither too hot nor too cold, just like the bear's porridge in the famous story.

The model developed by the team found that white dwarfs can fuel both processes simultaneously, making Earth-like planets possible around white dwarfs.

This discovery could help widen the focus of our search for life elsewhere in the cosmos, suggesting that systems that had previously been written off need to be revisited.

Related: The search for alien life

Expanding the boundary of Goldilocks zones

Habitable zones around stars are usually easy to define for stellar bodies like the sun and other main-sequence stars, which tend to have fairly stable temperatures over long periods of time. That isn't the case with white dwarfs, which form when stars like the sun run out of fuel for nuclear fusion, shedding their outer layers as their cores collapse and forming a cooling stellar ember.

Because these late-stage stellar bodies no longer have a source of fuel, they spend the rest of their existence gradually cooling, and that makes their temperatures and energy outputs inconsistent.

As a result, the Goldilocks zones around white dwarfs are constantly narrowing, with the distance that liquid water can exist without freezing on orbiting planets constantly shrinking around these dead stars.

Whyte and colleagues wanted to know if a planet orbiting a white dwarf in a constricting habitable zone could sustain processes that seem to be important for life for a period of seven billion years, the stretch that scientists have estimated is the maximum habitable lifetime of an Earth-like planet in this region around a star.

The team's model focused on two processes: photosynthesis, which plants use on Earth to convert sunlight, water and carbon dioxide into sugars, and ultraviolet (UV)-driven abiogenesis. This is the idea that UV radiation could help life arise — one of the theories that has been suggested to explain life taking root on Earth.

The model simulated an Earth-like planet orbiting a white dwarf, allowing the team to measure how much energy the world received as its dead star cooled and the habitable zone it sat in shrank.

Surprisingly, this revealed that, over the seven billion years, the simulated planet received enough energy to sustain both photosynthesis and UV-driven abiogenesis.

"That isn’t really common around most stars," Whyte said in a statement. “Something like the sun, of course, can provide enough energy, but brown dwarfs and red dwarfs smaller than the sun don’t really provide the energy in the UV and the photosynthesis range."

These findings could help scientists decide which systems to focus telescopes like the JWST on as humanity continues to search the cosmos for alien life. In particular, the results suggest that white dwarf systems may be worth a look as this hunt continues.

"We're giving them the confidence that these star systems are worth investing time and money into," Whyte said.

The team's results were published in December 2024 The Astrophysical Journal Letters.

NASA announced in July of last year that the rock, found in Mars' Jezero Crater by the agency's Perseverance rover, held some of the best evidence yet that ancient microbial life may have existed on the Red Planet billions of years ago, when it was significantly wetter than it is today. Earlier this week, scientists involved with the discovery presented their findings publicly for the first time this week at the Lunar and Planetary Science Conference in Texas, detailing the rock's chemical signatures and structures that continue to offer tantalizing hints of ancient Martian microbial life.

The fine-grained mudstone named Cheyava Falls, after the highest waterfall in Arizona's Grand Canyon, sits at the edge of an ancient river valley known as Neretva Vallis, which runs along the inner wall of the crater. The rock features spots of black, blue, or greenish hues, which the researchers have nicknamed "poppy seeds." Alongside these are dozens of dark-rimmed, millimeter-size splotches dubbed "leopard spots." Perseverance's instruments have revealed that several rocks hosting these two features are rich in iron, but that they vary in their oxidation states and redness — a telltale sign of activity by organic matter, which may have bleached the rocks of their red color.

"On Earth, reactions like these are commonly associated with microbially-driven organic matter respiration," Joel Hurowitz, the deputy principal investigator of the PIXL instrument located at the end of Perseverance's robotic arm, said at the conference.

Back in July, the discovery team had also noted the presence of calcium sulfate veins running through the rock, suggesting that water may have once flowed through it. While this and other features could point to non-biological processes, such as exposure to high temperatures from a volcanic event, ongoing analysis suggests the rock was never subjected to such heat or exposed to heat-related processes that would have caused it to recrystallize. "Everything seems to be consistent with low-temperature processes," Hurowitz said.

Scientists suspect the Neretva Vallis channel was carved out eons ago, by water gushing into the crater. One theory is that mud loaded with organic compounds was deposited into the valley, later cementing into the Cheyava Falls rock. Alternatively, a second water episode could have seeped into the rock after it had already formed, creating the features observed. "The rocks that we investigated appear to fill the Neretva Vallis channel," Hurowitz said.

There are no life-detection instruments onboard Perseverance, as its mission is to collect samples of scientific interest that will be returned to Earth for further scrutiny.

"As a community, we should feel compelled to do a whole lot of laboratory, field and modeling studies to try to investigate features like this in more detail," Hurowitz said. "And ultimately bring these samples back home so that we can reach a conclusion with regard to whether they were or were not formed by life."

However, details of the troubled Mars Sample Return effort remain uncertain after costs that ballooned to $11 billion led NASA to overhaul its approach and seek new ideas from its research centers, private industry and academia.

Former NASA administrator Bill Nelson announced earlier this year that the agency is leaving two options for the Trump administration to return to Earth 30 cigar-sized tubes containing bits of Mars that Perseverance has been collecting since 2021, including the Cheyava Falls sample. The two approaches differ in the way they would put hardware down on Mars, but either would require Congress to allocate $300 million to the mission for it to start launch proceedings by 2030 and return the samples between 2035 and 2039.

Scientists are eager to analyze the Cheyava Falls sample, as it could help answer one of humanity’s most profound questions: Are we alone in the universe?

"The discovery of life beyond Earth is so profound, so paradigm-shifting, you have to get it right," Amy Williams, an astrobiologist at the University of Florida who's on the Perseverance science team, had told Space.com shortly after the discovery. "Once you cross that line, you can't come back."

We don’t know for sure, but the answer is inextricably linked to the moment when water first materialized in the cosmos — and new simulations suggest the very first generation of stars helped form such life-giving water just 100 million to 200 million years after the Big Bang. This pushes back previous estimates by more than 500 million years.

"We were surprised that water could actually form so early on — even before the birth of the first galaxies," study co-author Muhammad Latif of the United Arab Emirates University told Space.com. The findings suggest that if some of this initial reservoir of water survived the heat-filled chaos of early galaxy formation, it could have been absorbed into newborn planets, potentially leading to habitable, water-rich worlds just a couple hundred million years after the Big Bang. "It's all connected with the story of how early life can start in the universe," Latif said.

Previous observations from the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile suggested that water existed about 780 million years after the Big Bang, when the young universe was chock-full of lightweight hydrogen and helium along with small amounts of lithium. These elements formed the first generation of stars, known to astronomers as Population III stars, which were enormous — up to dozens or even hundreds of times the mass of our sun — and lived notably short lives before dying as supernovas. Many of the universe's heavier elements, including oxygen, were forged within these stars through nuclear reactions and dispensed into space upon their deaths, where they were later incorporated into the next generation of stars.

To determine when water first formed in the universe, Latif and his colleagues used numerical models to trace the life cycles of two first-generation stars: one was 13 times heavier than our sun, and the other was 200 times heavier than our star. The smaller virtual star lived for 12.2 million years before dying in an explosive supernova, dumping about 0.051 solar masses of oxygen (nearly 17,000 Earth masses) into its surrounding space. The larger simulated star burned through its fuel in just 2.6 million years before meeting its own explosive end, showering a whopping 55 solar masses of oxygen (more than 18 million Earth masses) into space.

The simulations revealed that as shockwaves from each supernova radiated outward, turbulent density fluctuations created ripples that led some of the gas to coalesce into dense clumps. These leftover clumps, enriched by metals including oxygen ejected by supernovas, were likely the primary sites for water to form across the early universe.

Nestled within denser parts of the clouds, the water would have been protected from being destroyed by harsh radiation from nearby stars, Latif said. However, his team considered the simplest case of just one star forming in each clump, whereas theoretical simulations suggest multiple star systems to be the norm; more than half of all stars in the sky have one or more siblings. Multiple nearby stars would mean more dense, water-enriched clumps, but also a lot more radiation, which "might change a few things, but we still expect water might to survive," said Latif. "These are the first questions that we tried to answer, but we need more people to be working on this topic and explore this in more detail."

Follow-up simulations by his team suggest these water-harboring clumps are also favorable sites for habitable worlds to coalesce. Whether water within these clumps could have persisted through billions of years of cosmic evolution, and if so, how, is not yet fully understood. One leading theory suggests comets may have delivered water to Earth, but any such icy transporters from the early universe are not expected to have survived the harsh conditions of the Epoch of Reionization, said Latif, referring to a period about 400,000 years after the Big Bang when ionizing ultraviolet light from the first stars and galaxies pervaded the universe and lifted the primordial cosmic fog. However, the researchers are not yet ruling out the possibility that at least some of the water on Earth may be primordial in origin.

Populations of water-rich planets in the early universe would create faint emissions, Latif said, which could potentially be detected in the coming decade by ALMA or the forthcoming Square Kilometer Array in Australia and South Africa. If such emissions are indeed observed, it would be a "game changer," he said, in that it would shift the paradigm of origin of life to within just a couple hundred million years after the Big Bang.

"It opens a whole new line of research."

The study was published on Monday (March 3) in the journal Nature Astronomy.

New telescope technologies, including space-based tools such as the James Webb Telescope, have enabled us to discover thousands of potentially habitable exoplanets that could support life similar to that on Earth.

Gravitational wave detectors have opened a new avenue for space exploration by detecting space-time distortions caused by black holes and supernovae millions of light-years away.

Commercial space ventures have further accelerated these advancements, leading to increasingly sophisticated spacecraft and reusable rockets, signifying a new era in space exploration.

NASA’s OSIRIS-REx mission successfully touched down on asteroid Bennu when it was 207 million miles away from Earth and brought back rock and dust samples.

Several countries have developed the ability to deploy robots on the moon and Mars, with plans to send humans to these celestial bodies in the future.

A central driver of all these ambitious endeavours is still that fundamental question of whether life exists — or ever existed — elsewhere in the universe.

Defining life

Defining life is surprisingly challenging. While we intuitively recognize living organisms as having life, a precise definition remains elusive. Dictionaries offer various descriptions, such as the ability to grow, reproduce and respond to stimuli.

But, even these definitions can be ambiguous.

A more comprehensive definition considers life as a self-sustaining chemical system capable of processing information and maintaining a state of low entropy with little disorder or randomness.

Living things constantly require energy to sustain their molecular organization and maintain their highly organized structures and functions. Without this energy, life would quickly descend into chaos and disrepair. This definition encompasses the dynamic and complex nature of life, emphasizing its ability to adapt and evolve.

Life on Earth, as we currently understand it, is based on the interplay of DNA, RNA and proteins. DNA serves as the blueprint of life, containing the genetic instructions necessary for an organism’s development, survival and reproduction. These instructions are converted into messages that guide the production of proteins, the workhorses of the cell that are responsible for a vast array of functions.

This intricate system of DNA replication, protein synthesis and cellular processes — all based on long strings of molecules linked by carbon atoms — is fundamental to life on Earth. However, the universe may harbour life forms based on entirely different principles and biochemistries.

Something other than carbon

Life elsewhere could use different elements as building blocks. Silicon, with its chemical similarities to carbon, has been proposed as a potential alternative.

If they exist, silicon-based life forms may exhibit unique characteristics and adaptations. For instance, they might use silicon-based structures for support, analogous to bones or shells in carbon-based organisms.

Even though silicon-based organisms have not yet been found on Earth, silicon plays an important role in many existing life forms. It is an important secondary component for many plants and animals, serving structural and functional roles. For example, diatoms, a type of algae found in the ocean, feature glassy cell walls made of transparent silicon dioxide.

This doesn’t make diatoms silicon-based life forms, but it does prove silicon can indeed act as a building block of a living organism. But we still don’t know if silicon-based life forms exist at all, or what they would look like.

The origins of life on Earth

There are competing hypotheses on how life arose on Earth. One is that life’s building blocks were delivered on or in meteorites. The other is that those building blocks came together spontaneously via geochemistry in our planet’s early environment.

Meteorites have indeed been found to carry organic molecules, including amino acids, which are essential for life. It’s possible that organic molecules formed in deep space and were then brought to Earth by meteorites and asteroids.

On the other hand, geochemical processes on early Earth, such as those occurring in warm little ponds or in hydrothermal vents deep in the ocean, could have also provided the necessary conditions and ingredients for life to emerge.

However, no lab has yet been able to present a comprehensive, certain pathway to the formation of RNA, DNA and the first cellular life on Earth.

Many biological molecules are chiral, meaning they exist in two forms that are mirror images of each other, like left and right hands. While both left- and right-handed molecules are typically naturally produced in equal amounts, recent analyses of meteorites have revealed a slight asymmetry, favouring the left-handed form by as much as 60 percent.

This asymmetry in space-derived organic molecules is also observed in all biomolecules on Earth (proteins, sugars, amino acids, RNA and DNA), suggesting it could have arisen from the slight imbalance delivered from space, supporting the theory that life on Earth is extraterrestrial in origin.

Chances of life

The slight imbalance in chirality observed in many organic molecules could be an indicator that life on Earth originated from the delivery of organic molecules by extraterrestrial life. We could well be descendants of life that originated elsewhere.

The Drake equation, developed by astronomer Frank Drake in 1961, provides a framework for estimating the number of detectable civilizations within our galaxy.

This equation incorporates factors such as the rate of star formation, the fraction of stars with planets and calculates the fraction of those planets where intelligent life may emerge. An optimistic estimate using this formula suggests that 12,500 intelligent alien civilizations might exist in the Milky Way alone.

The primary argument for extraterrestrial life remains probabilistic: considering the sheer number of stars and planets, it seems highly improbable that life wouldn’t have arisen elsewhere.

The probability of humanity being the sole technological civilization in the observable universe is considered to be less than one in 10 billion trillion. Additionally, the chance of a civilization developing on any single habitable planet is better than one in 60 billion.

With an estimated 200 billion trillion stars in the observable universe, the existence of other technological species is highly likely, potentially even within our Milky Way galaxy.