Latest news with #Hycean
Yahoo
3 days ago
- General
- Yahoo
Astronomers thought they found signs of life on distant planet. New studies are skeptical
Back in April, the world became captivated by the news that maybe, just maybe, we weren't alone in the universe after all. If extraterrestrials were to exist on a distant exoplanet as a team of astronomers theorized, it wouldn't exactly be intelligent life, but – hey – it was something. The explosive findings came from a team of researchers at the University of Cambridge who studied data from NASA's James Webb Space Telescope to find molecules in the atmosphere of a planet known as K2-18b that could have been created by organisms akin to marine algae. But then along came other independent astronomers who took their own look at the data and came to their own highly skeptical conclusions. A series of studies since the April 17 announcement have cast doubt on the sensational claim that what the initial researchers had found was "the strongest evidence yet" that life exists anywhere else besides Earth. "The data we have so far is much too noisy for the proof that would be needed to make that claim,' Rafael Luque, an astronomer at the University of Chicago, who led the most recent study, said in a statement. 'There's just not enough certainty to say one way or the other.' Here's everything to know about K2-18b, and just what potential it has to harbor alien life. K2-18b, which orbits a red dwarf star more than 120 light-years from Earth, has for years intrigued astronomers who believe it could be among the best places to search for signs of extraterrestrial life. The cosmic body is an exoplanet, meaning it orbits a star outside of Earth's own solar system. First discovered in 2015 during NASA's planet-hunting K2 mission, K2-18b likely orbits its star in what astronomers refer to as the "habitable zone" – where conditions could allow for water. In a nod to the classic fairy tale, astronomers even refer to these regions as "Goldilocks" zones because conditions have to be just right – neither too hot nor too cold – for water to remain in liquid form and pool on planetary surfaces. Interestingly, K2-18b, which is 8.6 times bigger than Earth, isn't rocky like our planet. Rather, observations have allowed scientists to conclude that the exoplanet could be a Hycean world covered by ocean water underneath a hydrogen-rich atmosphere. Could alien life thrive on K2-18b? What to know about the distant exoplanet The latest findings on K2-18b came from a team of researchers led by Nikku Madhusudhan, an astrophysicist at the University of Cambridge in England. Because the planet is too far and too faint to observe directly with ground telescopes, astronomers had to get creative. In this case, the team studied data from the Webb Telescope gathered from observing K2-18b as the planet crossed in front of its star, causing starlight to filter through the planet's atmosphere. As the light passed through the planet's atmosphere, different amounts of light were blocked at different wavelengths, depending on what molecules are present. That's what led Madhusudhan and his team to detect hints of sulfur-based gases dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the atmosphere – both molecules from the same chemical family. On Earth, the gases are only produced by life, primarily microbial life such as marine algae like phytoplankton, according to the researchers. Since then, at least three different studies have largely dismissed the notion that any compelling evidence has been found to yet suggest life exists on K2-18b. In the most recent study led by Luque, researchers reviewed data from multiple observations of the planet. After combining observations of K2-18b in both the near-infrared light and longer wavelengths of mid-infrared light, the team concluded that it did not detect dimethyl sulfide. What's more, they found that other molecules, not just those possibly indicating signs of life, could explain the questionable discovery. In an earlier study published to arXiv, Jake Taylor, an astrophysicist at the University of Oxford, took a look at the Webb telescope data using a common data model for exoplanet studies and came to much the same conclusion: Taylor found no evidence of the atmospheric clues that were so integral in the Cambridge study's findings. Madhusudhan, who has issued rebuttals to some of the findings dismissing his potential discovery, has readily acknowledged that his team's observations are in need of further review. In announcing the findings, Madhusudhan conceded the molecules observed could have occurred by chance or could be the result of previously unknown chemical processes at work on K2-18b. Regardless, it appears astronomers all agree that we may not be as close as we thought to determining whether anything does indeed live on K2-18b. 'Answering whether there is life outside the solar system is the most important question of our field. It is why we are all studying these planets,' Luque said in a statement. 'We are making enormous progress in this field, and we don't want that to be overshadowed by premature declarations.' Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at elagatta@ This article originally appeared on USA TODAY: Planet K2-18b life signs discovery now in doubt
Yahoo
25-05-2025
- Science
- Yahoo
Scientists question possible signs of life on exoplanet K2-18b in new study: 'We never saw more than insignificant hints'
When you buy through links on our articles, Future and its syndication partners may earn a commission. In 2023, scientists from Cambridge University reported what appeared to be very exciting news. NASA's James Webb Space Telescope, they said, had detected signs of a liquid water ocean — and possibly life — on the exoplanet K2-18b, a temperate sub-Neptune world located about 124 light-years away from Earth. Then, earlier this year, the same team announced what they called even stronger evidence for those potential signs of alien life. 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 "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." 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 "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 "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. 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. Related Stories: — Doubts over signs of alien life on exoplanet K2-18b are rising: 'This is evidence of the scientific process at work' — Does exoplanet K2-18b host alien life or not? Here's why the debate continues — The pursuit of truths: A letter on the boy who cried aliens (op-ed) "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.
Mint
02-05-2025
- Science
- Mint
Untitled What are Hycean worlds, a proposed new habitat for life?
A little bit more than 124 light years from Earth, circling an otherwise uninteresting star in the constellation of Leo, sits a planet called K2-18 b. It is one of thousands of exoplanets spotted by Kepler, a space telescope that was launched in 2009 and is designed for the task. In 2019 observations by the Hubble Space Telescope suggested the planet might have water in its atmosphere; they were taken as evidence that, if it were a planet like the Earth, it might be habitable. On September 11th there was further astronomical hubbub, if also a few worries about potential hype, when a team led by Nikku Madhusudhan of the University of Cambridge announced that observations made with the more sensitive James Webb Space Telescope (JWST) suggested K2-18 b might be what is called a 'Hycean world'. What off Earth is that? Though the term (which is pronounced with a soft c) has a classical ring to it, it was introduced into astronomy by Dr Madhusudhan just two years ago, a portmanteau of 'hydrogen ocean'. It describes a kind of planet which is unknown in the solar system—but which might be both common and habitable elsewhere. Observations of exoplanets typically provide astronomers little more than an orbit, a mass and a radius. If the radius and mass match something seen in the solar system they can guess what the object's inner structure may be: an exoplanet the size and mass of the Earth is probably rocky. But with a radius 2.6 times that of the Earth, and a mass around nine times higher, K2-18 b is considerably bigger than any of the inner solar system's rocky planets. But it is also much smaller than the giants which hold sway in the outer solar system: just half the mass of Neptune, less than 3% the mass of Jupiter. With no nearby analogues to guide them, astronomers work out the structure of exoplanets from first principles: what physically self-consistent arrangement of shells of different densities can provide the right answer? The idea of a Hycean world is Dr Madhusudhan's suggestion for an answer which would apply to planets like K2-18 b. It imagines a core of rock and iron about the size of Earth that is covered by an ocean thousands of kilometres deep, topped off with a relatively thin atmosphere composed of light gas, presumably hydrogen. Give such a planet a mass like that of K2-18 b and it will have a radius like that of K2-18 b. It will also have a planet-covering, island- and continent-free ocean in which, in principle, life could thrive. JWST is sensitive enough to detect tiny flickers of starlight that have passed through the planet's uppermost atmosphere—and they are consistent with such a picture. Models predict the atmosphere of such a planet should contain carbon dioxide and methane, and both were found. There was also a tentative identification of dimethyl sulphide, a molecule which on Earth is only made by life, most notably by plankton. That does not mean that it is produced by life on K2-18 b. But the almost-observation is bound to pique interest. The sorts of processes which would produce methane in such an atmosphere should also produce ammonia, and this was not seen. But that is a Hycean feature, not a bug. Ammonia would dissolve in an underlying ocean in a way that methane would not, so only methane remains in the atmosphere. None of this, though, proves K2-18 b to be a true Hycean world. The depth of the atmosphere in Dr Madhusudhan's model is very important. If it is just a bit too thick, the resulting greenhouse effect would make liquid oceans impossible. Instead the lower reaches would consist of water in a very hot, high pressure, 'supercritical' state that is utterly uninhabitable. Sceptics say the existence of Hycean worlds is only possible given fine tuning which provides an atmosphere thick enough not to be lost to space but thin enough not to set off a runaway greenhouse effect in its depths. The new observations offer little—other than the absence of ammonia—to rule out the possibility that K2-18 b is just such a sauna hell world. Happily K2-18 b is not going anywhere, other than regularly round and round its parent star. There will be ample opportunities for further observations. Those should be able to show whether K2-18 b really is a habitable Hycean waterworld, and whether it really does have evocative traces of dimethyl sulphide in its atmosphere. If it does, you can expect to hear the word Hycean a lot more in years to come. First Published: 2 May 2025, 11:17 PM IST
Yahoo
30-04-2025
- Science
- Yahoo
Proof of life on K2-18b ‘not at all obvious': Harvard professor
Although scientists at the University of Cambridge suggest they have detected chemical signs of life on a planet 124 light years from Earth, a Harvard professor says there are problems with that theory. Avi Loeb, a Harvard professor of science and theoretical physicist, told NewsNation that while dimethyl sulfide and dimethyl disulfide appear to be present in the atmosphere of the planet K2-18b, that isn't necessarily proof of extraterrestrial life existing on the planet. Loeb said the molecule is produced by microorganisms in the Earth's oceans. However, K2-18b has a 1,000 times greater abundance of the molecule, which is also produced in comets, where no life exists, so far as is known. 'So, it is not at all obvious that if you find such a molecule in the atmosphere of a planet, it is indicative of life,' the professor said. K2-18b is an exoplanet that is nearly nine times the size of Earth, according to NASA. The Hycean exoplanet, which has the potential of possessing a hydrogen-rich atmosphere and an ocean-covered surface, was discovered in 2015, according to USA TODAY. While theories about whether life exists on K2-18b, Loeb said that the fundamental question becomes, just because the molecule exists in the atmosphere, does it guarantee that life is also present? Loeb noted to NewsNation he is much less excited about the discovery made by the Cambridge researchers than he would be about finding intelligent beings in the cosmos. 'An advanced civilization is someone that we can learn from,' Loeb continued, adding, 'It will be very likely that anywhere where you have liquid water, you also have the chemistry of life as we know it.' He said, 'I think we should hedge our bets and search for primitive forms of life and intelligent forms of life, because the evidence could be far more convincing if we find a gadget in our backyard that was produced by another civilization.' NewsNation's Michael Ramsey contributed reporting to this story Copyright 2025 Nexstar Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
The Hill
30-04-2025
- Science
- The Hill
Proof of life on K2-18b ‘not at all obvious': Harvard professor
Although scientists at the University of Cambridge suggest they have detected chemical signs of life on a planet 124 light years from Earth, a Harvard professor says there are problems with that theory. Avi Loeb, a Harvard professor of science and theoretical physicist, told NewsNation that while dimethyl sulfide and dimethyl disulfide appear to be present in the atmosphere of the planet K2-18b, that isn't necessarily proof of extraterrestrial life existing on the planet. Loeb said the molecule is produced by microorganisms in the Earth's oceans. However, K2-18b has a 1,000 times greater abundance of the molecule, which is also produced in comets, where no life exists, so far as is known. 'So, it is not at all obvious that if you find such a molecule in the atmosphere of a planet, it is indicative of life,' the professor said. K2-18b is an exoplanet that is nearly nine times the size of Earth, according to NASA. The Hycean exoplanet, which has the potential of possessing a hydrogen-rich atmosphere and an ocean-covered surface, was discovered in 2015, according to USA TODAY. While theories about whether life exists on K2-18b, Loeb said that the fundamental question becomes, just because the molecule exists in the atmosphere, does it guarantee that life is also present? Loeb noted to NewsNation he is much less excited about the discovery made by the Cambridge researchers than he would be about finding intelligent beings in the cosmos. 'An advanced civilization is someone that we can learn from,' Loeb continued, adding, 'It will be very likely that anywhere where you have liquid water, you also have the chemistry of life as we know it.' He said, 'I think we should hedge our bets and search for primitive forms of life and intelligent forms of life, because the evidence could be far more convincing if we find a gadget in our backyard that was produced by another civilization.'
