Latest news with #DMDS
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.
NDTV
24-05-2025
- Science
- NDTV
Doubt Cast On Claim Of 'Hints' Of Life On Faraway Planet
When astronomers announced last month they might have discovered the most promising hints of alien life yet on a distant planet, the rare good news raised hopes humanity could soon learn we are not alone in the universe. But several recent studies looking into the same data have found that there is not enough evidence to support such lofty claims, with one scientist accusing the astronomers of "jumping the gun". The debate revolves around the planet K2-18b, which is 124 light years away in the Leo constellation. The planet is thought to be the right distance from its star to have liquid water, making it a prime suspect in the search for extraterrestrial life. Last month, astronomers using the James Webb Space Telescope made headlines by announcing they had detected hints of the chemicals dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) on the planet. These chemicals are only produced by life such as marine algae on Earth, meaning they are considered potential "biosignatures" indicating life. The astronomers, led by Cambridge University's Nikku Madhusudhan, expressed caution about the "hints" of a biosignature, emphasising they were not claiming a definitive discovery. Their detection had reached a three-sigma level of statistical significance "which means there is still a three in 1,000 chance of this being a fluke," Madhusudhan said at the time. Biosignatures 'Vanish' Two of Madhusudhan's former students, Luis Welbanks of Arizona State University and Matthew Nixon of Maryland University, were among the researchers who have since re-analysed the data behind the announcement. When deploying other statistical models, "claims of a potential biosignature detection vanish", according to their preprint study published online late last month. Like the other papers since the April announcement, it has not been peer-reviewed. In one model, Welbanks and colleagues expanded the number of possible chemicals that could explain the signals detected by Webb to 90 from the original 20. More than 50 received a "hit", Welbanks told AFP. "When you detect everything, did you really detect anything?" he asked. They are not saying the planet definitely does not have DMS -- just that more observations are needed, Welbanks added. 'Arguments Are Healthy' Madhusudhan welcomed the robust debate, saying that remaining open to all possibilities is an essential part of the scientific method. "These sort of arguments are healthy," he told AFP. His team even went further, releasing their own preprint study last week that expanded the number of chemicals even further to 650. The three most "promising" chemicals they found included DMS but not DMDS -- a major part of the team's announcement in April. The other two chemicals were diethyl sulfide and methyl acrylonitrile, the latter of which is toxic. Madhusudhan admitted that these little-known chemicals are likely not "realistic molecules" for a planet like K2-18b. Welbanks pointed out that "in the span of a month -- with no new data, with no new models, with no new laboratory data -- their entire analysis changed". 'Closest We Have Ever Been' Telescopes observe such far-off exoplanets when they cross in front of their star, allowing astronomers to analyse how molecules block different wavelengths of light streaming through their atmosphere. Earlier this week, a paper led by Rafael Luque at the University of Chicago combined Webb's observations of K2-18b in both the near-infrared and mid-infrared wavelengths of light. It also found "no statistical significance for DMS or DMDS", the paper said. An earlier paper by Oxford astrophysicist Jake Taylor using a basic statistical test also found no strong evidence for any biosignatures. Madhusudhan dismissed the latter paper, saying the simple exercise did not account for observing physical phenomena. He also stood by his research, saying he was "just as confident" in the work as he was a month ago. More data about K2-18b will come in over the next year which should offer a much clearer picture, Madhusudhan added. Even if the planet does have DMS, it is not a guarantee of life -- the chemical has been detected on a lifeless asteroid. However, many researchers do believe that space telescopes could one day collect enough evidence to identify alien life from afar. "We are the closest we have ever been" to such a moment, Welbanks said. "But we have to use the frameworks that are in place and build up (evidence) in a reliable method, rather than using non-standard practices and jumping the gun -- as has been done in this particular case," Nixon added.
Straits Times
24-05-2025
- Science
- Straits Times
Doubt cast on claim of ‘hints' of life on faraway planet
The debate revolves around the planet K2-18b, which is 124 light years away. PHOTO: AFP Doubt cast on claim of 'hints' of life on faraway planet PARIS - When astronomers announced in April they might have discovered the most promising hints of alien life yet on a distant planet, the rare good news raised hopes humanity could soon learn we are not alone in the universe. But several recent studies looking into the same data have found that there is not enough evidence to support such lofty claims, with one scientist accusing the astronomers of 'jumping the gun'. The debate revolves around the planet K2-18b, which is 124 light years away in the Leo constellation. The planet is thought to be the right distance from its star to have liquid water, making it a prime suspect in the search for extraterrestrial life. In April , astronomers using the James Webb Space Telescope made headlines by announcing they had detected hints of the chemicals dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) on the planet. These chemicals are only produced by life such as marine algae on Earth, meaning they are considered potential 'biosignatures' indicating life. The astronomers, led by Cambridge University's Nikku Madhusudhan, expressed caution about the 'hints' of a biosignature, emphasising they were not claiming a definitive discovery. Their detection had reached a three-sigma level of statistical significance 'which means there is still a three in 1,000 chance of this being a fluke', Dr Madhusudhan said at the time. Biosignatures 'vanish' Two of Dr Madhusudhan's former students, Dr Luis Welbanks of Arizona State University and Dr Matthew Nixon of Maryland University, were among the researchers who have since re-analysed the data behind the announcement. When deploying other statistical models, 'claims of a potential biosignature detection vanish', according to their preprint study published online late in April . Like the other papers since the April announcement, it has not been peer-reviewed. In one model, Dr Welbanks and colleagues expanded the number of possible chemicals that could explain the signals detected by Webb to 90 from the original 20. More than 50 received a 'hit', Dr Welbanks told AFP. 'When you detect everything, did you really detect anything?' he asked. They are not saying the planet definitely does not have DMS – just that more observations are needed, Dr Welbanks added. 'Arguments are healthy' Dr Madhusudhan welcomed the robust debate, saying that remaining open to all possibilities is an essential part of the scientific method. 'These sort of arguments are healthy,' he told AFP. His team even went further, releasing their own preprint study last week that expanded the number of chemicals even further to 650. The three most 'promising' chemicals they found included DMS but not DMDS – a major part of the team's announcement in April. The other two chemicals were diethyl sulfide and methyl acrylonitrile, the latter of which is toxic. Dr Madhusudhan admitted that these little-known chemicals are likely not 'realistic molecules' for a planet like K2-18b. Dr Welbanks pointed out that 'in the span of a month – with no new data, with no new models, with no new laboratory data – their entire analysis changed'. 'Closest we have ever been' Telescopes observe such far-off exoplanets when they cross in front of their star, allowing astronomers to analyse how molecules block different wavelengths of light streaming through their atmosphere. Earlier this week, a paper led by Dr Rafael Luque at the University of Chicago combined Webb's observations of K2-18b in both the near-infrared and mid-infrared wavelengths of light. It also found 'no statistical significance for DMS or DMDS', the paper said. An earlier paper by Oxford astrophysicist Jake Taylor using a basic statistical test also found no strong evidence for any biosignatures. Dr Madhusudhan dismissed the latter paper, saying the simple exercise did not account for observing physical phenomena. He also stood by his research, saying he was 'just as confident' in the work as he was a month ago. More data about K2-18b will come in over the next year which should offer a much clearer picture, Dr Madhusudhan added. Even if the planet does have DMS, it is not a guarantee of life – the chemical has been detected on a lifeless asteroid. However, many researchers do believe that space telescopes could one day collect enough evidence to identify alien life from afar. 'We are the closest we have ever been' to such a moment, Dr Welbanks said. 'But we have to use the frameworks that are in place and build up (evidence) in a reliable method, rather than using non-standard practices and jumping the gun – as has been done in this particular case,' Dr Nixon added. AFP Join ST's Telegram channel and get the latest breaking news delivered to you.
Time of India
24-05-2025
- Science
- Time of India
Doubt cast on claim of 'hints' of life on faraway planet
Representative Image PARIS: When astronomers announced last month they might have discovered the most promising hints of alien life yet on a distant planet, the rare good news raised hopes humanity could soon learn we are not alone in the universe. But several recent studies looking into the same data have found that there is not enough evidence to support such lofty claims, with one scientist accusing the astronomers of "jumping the gun". The debate revolves around the planet K2-18b , which is 124 light years away in the Leo constellation. The planet is thought to be the right distance from its star to have liquid water, making it a prime suspect in the search for extraterrestrial life . by Taboola by Taboola Sponsored Links Sponsored Links Promoted Links Promoted Links You May Like Trade Bitcoin & Ethereum – No Wallet Needed! IC Markets Start Now Undo Last month, astronomers using the James Webb Space Telescope made headlines by announcing they had detected hints of the chemicals dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) on the planet. These chemicals are only produced by life such as marine algae on Earth, meaning they are considered potential " biosignatures " indicating life. The astronomers, led by Cambridge University's Nikku Madhusudhan , expressed caution about the "hints" of a biosignature, emphasising they were not claiming a definitive discovery. Their detection had reached a three-sigma level of statistical significance "which means there is still a three in 1,000 chance of this being a fluke," Madhusudhan said at the time. Biosignatures 'vanish' Two of Madhusudhan's former students, Luis Welbanks of Arizona State University and Matthew Nixon of Maryland University, were among the researchers who have since re-analysed the data behind the announcement. When deploying other statistical models, "claims of a potential biosignature detection vanish", according to their preprint study published online late last month. Like the other papers since the April announcement, it has not been peer-reviewed. In one model, Welbanks and colleagues expanded the number of possible chemicals that could explain the signals detected by Webb to 90 from the original 20. More than 50 received a "hit", Welbanks told AFP. "When you detect everything, did you really detect anything?" he asked. They are not saying the planet definitely does not have DMS -- just that more observations are needed, Welbanks added. 'Arguments are healthy' Madhusudhan welcomed the robust debate, saying that remaining open to all possibilities is an essential part of the scientific method. "These sort of arguments are healthy," he told AFP. His team even went further, releasing their own preprint study last week that expanded the number of chemicals even further to 650. The three most "promising" chemicals they found included DMS but not DMDS -- a major part of the team's announcement in April. The other two chemicals were diethyl sulfide and methyl acrylonitrile, the latter of which is toxic. Madhusudhan admitted that these little-known chemicals are likely not "realistic molecules" for a planet like K2-18b. Welbanks pointed out that "in the span of a month -- with no new data, with no new models, with no new laboratory data -- their entire analysis changed". ' Closest we have ever been' Telescopes observe such far-off exoplanets when they cross in front of their star, allowing astronomers to analyse how molecules block different wavelengths of light streaming through their atmosphere. Earlier this week, a paper led by Rafael Luque at the University of Chicago combined Webb's observations of K2-18b in both the near-infrared and mid-infrared wavelengths of light. It also found "no statistical significance for DMS or DMDS", the paper said. An earlier paper by Oxford astrophysicist Jake Taylor using a basic statistical test also found no strong evidence for any biosignatures. Madhusudhan dismissed the latter paper, saying the simple exercise did not account for observing physical phenomena. He also stood by his research, saying he was "just as confident" in the work as he was a month ago. More data about K2-18b will come in over the next year which should offer a much clearer picture, Madhusudhan added. Even if the planet does have DMS, it is not a guarantee of life -- the chemical has been detected on a lifeless asteroid. However, many researchers do believe that space telescopes could one day collect enough evidence to identify alien life from afar. "We are the closest we have ever been" to such a moment, Welbanks said. "But we have to use the frameworks that are in place and build up (evidence) in a reliable method, rather than using non-standard practices and jumping the gun -- as has been done in this particular case," Nixon added.
Yahoo
09-05-2025
- Science
- Yahoo
Why Astronomers Doubt Claims That Planet K2-18 b Finding Means Alien Life
A University of Cambridge-led team of astronomers made worldwide headlines last night with claims that they had found the 'strongest hints yet of biological activity outside the Solar System'. The discovery involves a distant planet known as K2-18 b, which the team says has one or more molecules in its atmosphere that might have been generated by living things. The announcement has been met with floods of scepticism from other researchers who study such 'biosignatures' in exoplanet atmospheres. 'It is not strong evidence,' says Stephen Schmidt, an astronomer at Johns Hopkins University in Baltimore, Maryland. 'It's almost certainly not life,' says Tessa Fisher, an astrobiologist at the University of Arizona in Tucson. [Sign up for Today in Science, a free daily newsletter] Here, Nature explores the high-profile claim — and why many scientists say it's far from proof of alien life. Using the James Webb Space Telescope (JWST), the Cambridge team reported finding hints of the molecule dimethyl sulfide (DMS), a pungent smelling compound that can be produced by bacteria, in the atmosphere of K2-18 b, a planet smaller than Neptune that lies about 38 parsecs from Earth. The scientists detected the molecule by analysing starlight as it filtered through the planet's atmosphere; different chemical compounds leave identifying imprints in the light's spectrum. The data might indicate the presence of the related molecule dimethyl disulfide (DMDS), either in addition to DMS or in its stead. These chemicals are intriguing because on Earth they are produced by living organisms such as marine phytoplankton. In 2023, the researchers reported similar findings. This follow-up work looks at the planet in a different set of wavelengths and is a stronger and cleaner signal that the molecules are present, the team says. Being able to tease out the detailed chemistry of a faraway planet is a technical tour-de-force, the researchers say. 'What we are seeing is a major paradigm shift in the field of exoplanet science,' said team leader Nikku Madhusudhan, an astronomer at Cambridge, in a livestreamed colloquium on 17 April. He did not respond to a request for an interview before press time for this story. Scientists have been looking for life beyond Earth for centuries. If DMS and DMDS do exist in this planet's atmosphere, and if they are formed by biological activity, it would represent a groundbreaking moment in the search for extraterrestrial life. The work also marks a step toward understanding planets like K2-18 b, which are some of the most common of the 5,800-plus planets that have so far been identified throughout the universe. They are referred to as 'mini Neptunes' based on their mass, but beyond that, little is known about their makeup. Some researchers, including Madhusudhan's team, say that some could be exotic water worlds cloaked in hydrogen atmospheres. If so, they may be some of the best places to look for the existence of extraterrestrial life. For starters, there are questions about whether K2-18 b even has water — or a surface where anything could live. Modelling studies of it and similar planets suggest that they are probably barren. 'A lifeless mini-Neptune scenario remains the most parsimonious explanation,' says Joshua Krissansen-Totton, a planetary scientist at the University of Washington in Seattle. Then there's the issue of whether DMS/DMDS is actually present, or whether it is a spurious signal. The measurement reported by the Cambridge team is 'really pushing the limit of what JWST can do,' says Laura Kreidberg, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany. Schmidt and his colleagues recently re-analysed the 2023 claim from the Cambridge team and found no evidence of biosignature molecules in that data. Schmidt says the new observations are 'pretty noisy, and any reported features could still just be statistical fluctuations'. For their part, the Cambridge researchers say there is just a 0.3% probability that the signal could be due to chance. Finally, if the DMS/DMDS signal is indeed real, then there are many additional questions that need to be resolved before it could be attributed to life, other researchers say. For instance, laboratory experiments have shown that DMS can be made through abiotic processes — those not involving life. 'We know very little about the chemistry of these atmospheres,' says Eleanor Browne, a chemist at the University of Colorado Boulder who led that recent study. Others have reported that DMS is present on a comet explored by the European Space Agency, which definitely does not have life on it. 'The planetary context is what matters,' says Edward Schweiterman, an astrobiologist at the University of California Riverside. If the molecules really are in the planet's atmosphere, he says, 'we have to brainstorm novel ways of producing a lot of it through abiotic means and evaluate those possibilities before accepting it as evidence for life.' Madhusudhan and his colleagues hope to get more observing time with JWST to help nail down the statistical significance of their claim. Beyond that, says Schweiterman, 'what you'd like to see is validation from multiple independent groups.' Regardless of how the claim plays out, it highlights the importance of studying planets like K2-18 b, Kreidberg says: 'This is a very, very rich playground for us to understand how planetary atmospheres work.' This article is reproduced with permission and was first published on April 17, 2025.
