Latest news with #K2-18b
CNN
07-06-2025
- Science
- CNN
Moon lander is lost on second bid at touchdown by Tokyo-based company
As scientists search for worlds that may be habitable for life, they've discovered a type that is common in the universe — but doesn't exist in our own solar system. These enigmatic planets are called sub-Neptunes, which are larger than Earth but smaller than Neptune. An April study catapulted one such world, named K2-18b, into the spotlight. Astronomers at the University of Cambridge claimed they detected molecules in the planet's atmosphere that might be biosignatures — markers of biological activity that could hint at past or present life. Now, other groups of astronomers have looked at the same data and disagree with the findings, saying there is more to the story. The twists and turns in the ongoing conversation around planet K2-18b showcase why the search for evidence of life beyond Earth is so difficult. Indeed, persistence is everything when it comes to space investigation. 'Never quit the lunar quest' was the motto underpinning a high-stakes mission that aimed to touch down on the moon Thursday. But Tokyo-based Ispace lost contact with its vehicle at the time it should have landed. The Resilience spacecraft was Ispace's second bid at a soft lunar landing. The company's previous try with the Hakuto-R lunar lander crashed into the moon in April 2023. 'This is our second failure, and about these results, we have to really take it seriously,' said Ispace CEO Takeshi Hakamada of the nail-biting attempt. Ispace has its work cut out for it, but it isn't giving up. New research combining artificial intelligence with radiocarbon dating is changing the way scholars think about the Dead Sea Scrolls. Bedouin shepherds first spotted the scrolls in 1947 within a cave in the Judaean Desert. Archaeologists then recovered thousands of scroll fragments, including the oldest copies of the Hebrew Bible, from 11 caves near the site of Khirbat Qumran. 'They completely changed the way we think about ancient Judaism and early Christianity,' said lead study author Mladen Popović, a dean at the University of Groningen in the Netherlands. Scholars thought the roughly 1,000 manuscripts, written mostly on parchment and papyrus, ranged from the third century BC to the second century AD. But some of the scrolls, which serve as a crucial intellectual time capsule, could be much older, the new analysis suggests. A World War I-era submarine was lost at sea off California's coast nearly 108 years ago, killing 19 crew members. Now, researchers from the Woods Hole Oceanographic Institution have captured never-before-seen deep-sea imagery of the wreckage. The plague pandemic known as the Black Death killed at least 25 million people across medieval Europe over five years. The culprit behind the disease is a bacterium called Yersinia pestis, which has led to three major plague outbreaks since the first century AD — and it still exists today. How has the plague persisted for centuries? Changes to one gene in the bacterium created new, less deadly strains that kept hosts alive longer so it could keep spreading. The weaker strains have since gone extinct, according to new research. But the findings could yield key clues to help scientists manage the current bacterium's dominant lineage, which is of the deadlier variety. If you've ever walked through a fruit orchard, you might have been steps away from a living tower of worms. That's what researchers from the Max Planck Institute of Animal Behavior and the University of Konstanz in Germany found when they inspected rotten pears and apples. Hundreds of the microscopic worms, called nematodes, climbed on top of one another to form structures 10 times their size — even making a twisting 'arm' to sense the environment — leading scientists to question what's driving the behavior. 'What we got was more than just some worms standing on top of each other,' said senior study author Serena Ding, a Max Planck research group leader of genes and behavior. 'It's a coordinated superorganism, acting and moving as a whole.' These stories will pique your curiosity: — For over a century, astronomers thought the Milky Way and Andromeda galaxies would collide in 4.5 billion years, but new telescope observations may change that. However, another galaxy could entangle with ours sooner. — Archaeologists who uncovered the remains of an ancient Mayan complex in Guatemala named the site after two humanlike rock figures that are believed to represent an 'ancestral couple,' according to the country's Ministry of Culture and Sport. — A fossil of the earliest known bird that was kept in a private collection for decades has provided scientists with 'one 'Wow!' after another,' including the first flight feathers seen in an Archaeopteryx specimen, said Dr. Jingmai O'Connor, associate curator of fossil reptiles at the Field Museum.
Yahoo
06-06-2025
- Science
- Yahoo
A surprising study revealed biological activity on a distant planet. Weeks later, scientists say there's more to the story
Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. A tiny sign revealed in April seemed like it might change the universe as we know it. Astronomers had detected just a hint, a glimmer of two molecules swirling in the atmosphere of a distant planet called K2-18b — molecules that on Earth are produced only by living things. It was a tantalizing prospect: the most promising evidence yet of an extraterrestrial biosignature, or traces of life linked to biological activity. But only weeks later, new findings suggest the search must continue. 'It was exciting, but it immediately raised several red flags because that claim of a potential biosignature would be historic, but also the significance or the strength of the statistical evidence seemed to be too high for the data,' said Dr. Luis Welbanks, a postdoctoral research scholar at Arizona State University's School of Earth and Space Exploration. While the molecules identified on K2-18b by the April study — dimethyl sulfide, or DMS, and dimethyl disulfide, or DMDS — are associated largely with microbial organisms on our planet, scientists point out that the compounds can also form without the presence of life. Now, three teams of astronomers not involved with the research, including Welbanks, have assessed the models and data used in the original biosignature discovery and got very different results, which they have submitted for peer review. Meanwhile, the lead author of the April study, Nikku Madhusudhan, and his colleagues have conducted additional research that they say reinforces their previous finding about the planet. And it's likely that additional observations and research from multiple groups of scientists are on the horizon. The succession of research papers revolving around K2-18b offers a glimpse of the scientific process unfolding in real time. It's a window into the complexities and nuances of how researchers search for evidence of life beyond Earth — and shows why the burden of proof is so high and difficult to reach. Located 124 light-years from Earth, K2-18b is generally considered a worthy target to scour for signs of life. It is thought to be a Hycean world, a planet entirely covered in liquid water with a hydrogen-rich atmosphere, according to previous research led by Madhusudhan, a professor of astrophysics and exoplanetary science at the University of Cambridge's Institute of Astronomy. And as such, K2-18b has rapidly attracted attention as a potentially habitable place beyond our solar system. Convinced of K2-18b's promise, Madhusudhan and his Cambridge colleagues used observations of the planet by the largest space telescope in operation, the James Webb Space Telescope, to study the planet further. But two scientists at the University of Chicago — Dr. Rafael Luque, a postdoctoral scholar in the university's department of astronomy and astrophysics, and Michael Zhang, a 51 Pegasi b / Burbidge postdoctoral fellow — spotted some problems with what they found. After reviewing Madhusudhan and his team's April paper, which followed up on their 2023 research, Luque and Zhang noticed that the Webb data looked 'noisy,' Luque said. Noise, caused by imperfections in the telescope and the rate at which different particles of light reach the telescope, is just one challenge astronomers face when they study distant exoplanets. Noise can distort observations and introduce uncertainties into the data, Zhang said. Trying to detect specific gases in distant exoplanet atmospheres introduces even more uncertainty. The most noticeable features from a gas like dimethyl sulfide stem from a bond of hydrogen and carbon molecules — a connection that can stretch and bend and absorb light at different wavelengths, making it hard to definitively detect one kind of molecule, Zhang said. 'The problem is basically every organic molecule has a carbon-hydrogen bond,' Zhang said. 'There's hundreds of millions of those molecules, and so these features are not unique. If you have perfect data, you can probably distinguish between different molecules. But if you don't have perfect data, a lot of molecules, especially organic molecules, look very similar, especially in the near-infrared.' Delving further into the paper, Luque and Zhang also noticed that the perceived temperature of the planet appeared to increase sharply from a range of about 250 Kelvin to 300 Kelvin (-9.67 F to 80.33 F or -23.15 C to 26.85 C) in research Madhusudhan published in 2023 to 422 Kelvin (299.93 F or 148.85 C) in the April study. Such harsh temperatures could change the way astronomers think about the planet's potential habitability, Zhang said, especially because cooler temperatures persist in the top of the atmosphere — the area that Webb can detect — and the surface or ocean below would likely have even higher temperatures. 'This is just an inference only from the atmosphere, but it would certainly affect how we think about the planet in general,' Luque said. Part of the issue, he said, is that the April analysis didn't include data collected from all three Webb instruments Madhusudhan's team used over the past few years. So Luque, Zhang and their colleagues conducted a study combining all the available data to see whether they could achieve the same results, or even find a higher amount of dimethyl sulfide. They found 'insufficient evidence' of both molecules in the planet's atmosphere. Instead, Luque and Zhang's team spotted other molecules, like ethane, that could fit the same profile. But ethane does not signify life. Arizona State's Welbanks and his colleagues, including Dr. Matt Nixon, a postdoctoral researcher in the department of astronomy at the University of Maryland College Park, also found what they consider a fundamental problem with the April paper on K2-18b. The concern, Welbanks said, was with how Madhusudhan and his team created models to show which molecules might be in the planet's atmosphere. 'Each (molecule) is tested one at a time against the same minimal baseline, meaning every single model has an artificial advantage: It is the only explanation permitted,' Welbanks said. When Welbanks and his team conducted their own analysis, they expanded the model from Madhusudhan's study. '(Madhusudhan and his colleagues) didn't allow for any other chemical species that could potentially be producing these small signals or observations,' Nixon said. 'So the main thing we wanted to do was assess whether other chemical species could provide an adequate fit to the data.' When the model was expanded, the evidence for dimethyl sulfide or dimethyl disulfide 'just disappears,' Welbanks said. Madhusudhan believes the studies that have come out after his April paper are 'very encouraging' and 'enabling a healthy discussion on the interpretation of our data on K2-18b.' He reviewed Luque and Zhang's work and agreed that their findings don't show a 'strong detection for DMS or DMDS.' When Madhusudhan's team published the paper in April, he said the observations reached the three-sigma level of significance, or a 0.3% probability that the detections occurred by chance. For a scientific discovery that is highly unlikely to have occurred by chance, the observations must meet a five-sigma threshold, or below a 0.00006% probability that the observations occurred by chance. Meeting such a threshold will require many steps, Welbanks said, including repeated detections of the same molecule using multiple telescopes and ruling out potential nonbiological sources. While such evidence could be found in our lifetime, it is less likely to be a eureka moment and more a slow build requiring a consensus among astronomers, physicists, biologists and chemists. 'We have never reached that level of evidence in any of our studies,' Madhusudhan wrote in an email. 'We have only found evidence at or below 3-sigma in our two previous studies (Madhusudhan et al. 2023 and 2025). We refer to this as moderate evidence or hints but not a strong detection. I agree with (Luque and Zhang's) claim which is consistent with our study and we have discussed the need for stronger evidence extensively in our study and communications.' In response to the research conducted by Welbanks' team, Madhusudhan and his Cambridge colleagues have authored another manuscript expanding the search on K2-18b to include 650 types of molecules. They have submitted the new analysis for peer review. 'This is the largest search for chemical signatures in an exoplanet to date, using all the available data for K2-18b and searching through 650 molecules,' Madhusudhan said. 'We find that DMS continues to be a promising candidate molecule in this planet, though more observations are required for a firm detection as we have noted in our previous studies.' Welbanks and Nixon were pleased that Madhusudhan and his colleagues addressed the concerns raised but feel that the new paper effectively walks back central claims made in the original April study, Welbanks said. 'The new paper tacitly concedes that the DMS/DMDS detection was not robust, yet still relies on the same flawed statistical framework and a selective reading of its own results,' Welbanks said in an email. 'While the tone is more cautious (sometimes), the methodology continues to obscure the true level of uncertainty. The statistical significance claimed in earlier work was the product of arbitrary modeling decisions that are not acknowledged.' Luque said the Cambridge team's new paper is a step in the right direction because it explores other possible chemical biosignatures. 'But I think it fell short in the scope,' Luque said. 'I think it restricted itself too much into being a rebuttal to the (Welbanks) paper.' Separately, however, the astronomers studying K2-18b agree that pushing forward on researching the exoplanet contributes to the scientific process. 'I think it's just a good, healthy scientific discourse to talk about what is going on with this planet,' Welbanks said. 'Regardless of what any single author group says right now, we don't have a silver bullet. But that is exactly why this is exciting, because we know that we're the closest we have ever been (to finding a biosignature), and I think we may get it within our lifetime, but right now, we're not there. That is not a failure. We're testing bold ideas.'
CTV News
06-06-2025
- Science
- CTV News
A surprising study revealed biological activity on a distant planet. Weeks later, scientists say there's more to the story
An artist's concept shows what K2-18b might look like. Thought to be covered entirely in liquid water with a hydrogen-rich atmosphere, the exoplanet may be a good place to look for biological activity. A tiny sign revealed in April seemed like it might change the universe as we know it. Astronomers had detected just a hint, a glimmer of two molecules swirling in the atmosphere of a distant planet called K2-18b — molecules that on Earth are produced only by living things. It was a tantalizing prospect: the most promising evidence yet of an extraterrestrial biosignature, or traces of life linked to biological activity. But only weeks later, new findings suggest the search must continue. 'It was exciting, but it immediately raised several red flags because that claim of a potential biosignature would be historic, but also the significance or the strength of the statistical evidence seemed to be too high for the data,' said Dr. Luis Welbanks, a postdoctoral research scholar at Arizona State University's School of Earth and Space Exploration. While the molecules identified on K2-18b by the April study — dimethyl sulfide, or DMS, and dimethyl disulfide, or DMDS — are associated largely with microbial organisms on our planet, scientists point out that the compounds can also form without the presence of life. Now, three teams of astronomers not involved with the research, including Welbanks, have assessed the models and data used in the original biosignature discovery and got very different results, which they have submitted for peer review. Meanwhile, the lead author of the April study, Nikku Madhusudhan, and his colleagues have conducted additional research that they say reinforces their previous finding about the planet. And it's likely that additional observations and research from multiple groups of scientists are on the horizon. The succession of research papers revolving around K2-18b offers a glimpse of the scientific process unfolding in real time. It's a window into the complexities and nuances of how researchers search for evidence of life beyond Earth — and shows why the burden of proof is so high and difficult to reach. Noisy data Located 124 light-years from Earth, K2-18b is generally considered a worthy target to scour for signs of life. It is thought to be a Hycean world, a planet entirely covered in liquid water with a hydrogen-rich atmosphere, according to previous research led by Madhusudhan, a professor of astrophysics and exoplanetary science at the University of Cambridge's Institute of Astronomy. And as such, K2-18b has rapidly attracted attention as a potentially habitable place beyond our solar system. Convinced of K2-18b's promise, Madhusudhan and his Cambridge colleagues used observations of the planet by the largest space telescope in operation, the James Webb Space Telescope, to study the planet further. But two scientists at the University of Chicago — Dr. Rafael Luque, a postdoctoral scholar in the university's department of astronomy and astrophysics, and Michael Zhang, a 51 Pegasi b / Burbidge postdoctoral fellow — spotted some problems with what they found. After reviewing Madhusudhan and his team's April paper, which followed up on their 2023 research, Luque and Zhang noticed that the Webb data looked 'noisy,' Luque said. Noise, caused by imperfections in the telescope and the rate at which different particles of light reach the telescope, is just one challenge astronomers face when they study distant exoplanets. Noise can distort observations and introduce uncertainties into the data, Zhang said. Trying to detect specific gases in distant exoplanet atmospheres introduces even more uncertainty. The most noticeable features from a gas like dimethyl sulfide stem from a bond of hydrogen and carbon molecules — a connection that can stretch and bend and absorb light at different wavelengths, making it hard to definitively detect one kind of molecule, Zhang said. 'The problem is basically every organic molecule has a carbon-hydrogen bond,' Zhang said. 'There's hundreds of millions of those molecules, and so these features are not unique. If you have perfect data, you can probably distinguish between different molecules. But if you don't have perfect data, a lot of molecules, especially organic molecules, look very similar, especially in the near-infrared.'
Sustainability Times
06-06-2025
- Science
- Sustainability Times
'I Was Convinced We'd Found Aliens': Scientists Backtrack on K2-18b Breakthrough Before Revealing the Devastating Truth
IN A NUTSHELL 🔍 Researchers re-examined data on K2-18b , broadening the pool of atmospheric chemicals from 20 to 90, weakening earlier claims of alien life. , broadening the pool of atmospheric chemicals from 20 to 90, weakening earlier claims of alien life. 🌌 Initial excitement was sparked by the detection of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), considered potential biosignatures. and dimethyl disulfide (DMDS), considered potential biosignatures. 📊 Updated studies found no statistically significant evidence of these compounds, highlighting the need for robust scientific methods . . 🔭 Advanced technology and future observations are crucial for gaining a clearer understanding of exoplanetary atmospheres and the potential for life. In recent years, the search for extraterrestrial life has captivated scientists and the public alike, with the focus often landing on distant exoplanets like K2-18b. Located 124 light-years away in the Leo constellation, this intriguing planet resides within the habitable zone of its star, sparking hope for the potential presence of life. However, recent research has cast doubt on earlier claims of alien life signs on K2-18b, urging scientists to remain cautious. This article delves into the ongoing debate, examining updated data, scientific methodologies, and the future of such explorations. Re-evaluating the Evidence: A Shift in Perspective The initial excitement over potential biosignatures on K2-18b stemmed from the detection of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) by astronomers using the James Webb Space Telescope. These compounds, known to be produced by marine algae on Earth, were considered potential indicators of life. However, a re-examination of the data by researchers, including former students of Nikku Madhusudhan, has altered this perspective. By broadening the pool of possible atmospheric chemicals from 20 to 90, the team found that the signals no longer uniquely pointed to biological explanations. Madhusudhan and his colleagues highlighted the necessity of employing alternative statistical models to re-evaluate the evidence. Their updated approach included a list of 650 potential atmospheric chemicals, underscoring the complexity of identifying biosignatures. This re-evaluation has significantly weakened the case for a biological explanation, illustrating the importance of skepticism and thorough analysis in scientific discovery. 'Super-Earths Are Everywhere': New Study Reveals These Giant Alien Worlds Are Far More Common Than Scientists Ever Imagined Scientific Methodologies: The Quest for Precision The search for life on exoplanets like K2-18b relies heavily on precise scientific methodologies. Astronomers analyze distant planets by observing their transit across host stars, which allows them to study how molecules in the atmosphere absorb specific wavelengths of starlight. This method, while powerful, is fraught with challenges. Recent studies combining observations in both near-infrared and mid-infrared wavelengths found no statistically significant evidence for DMS or DMDS, further complicating the case for life. Postdoctoral researcher Rafael Luque and Oxford astrophysicist Jake Taylor contributed to this discourse by employing different statistical methods. Taylor's basic statistical approach found no strong signs of biosignatures, emphasizing the need for robust methods and comprehensive data. The inconsistencies in findings highlight the complexities involved in interpreting astronomical data, urging scientists to continuously refine their techniques. 'Doomsday Coming Sooner Than You Think': This Groundbreaking Study Reveals the Imminent Threat Facing Humanity and Why We Need to Act Now The Role of Advanced Technology in Space Exploration Advanced technology plays a pivotal role in unraveling the mysteries of distant exoplanets. The James Webb Space Telescope, with its ability to capture detailed atmospheric data, has been instrumental in the ongoing research of K2-18b. However, as Madhusudhan pointed out, more data is needed to draw definitive conclusions. As technology evolves, so too does the precision and scope of astronomical research. Future observations, made possible by technological advancements, will enhance our understanding of planets like K2-18b. As more data is collected over the next year, scientists hope to paint a clearer picture of the atmospheric composition and potential for life. This ongoing technological evolution promises to deepen our knowledge of the universe and our place within it. 'They're Coming From Space!': Mysterious Radio Signals Repeating Every 2 Hours Identified in That Distant Star System Looking Forward: The Future of Exoplanetary Research As the debate over K2-18b continues, the scientific community remains committed to uncovering the truth about alien life. The conflicting findings underscore the need for a cautious approach, where claims are rigorously tested and re-tested. The journey to discover extraterrestrial life is a marathon, not a sprint, demanding patience and perseverance. Looking forward, the collection of new data and the refinement of analytical methods will be crucial. The pursuit of knowledge about exoplanets like K2-18b serves as a reminder of humanity's insatiable curiosity and the endless possibilities that lie beyond our home planet. As we continue to explore the cosmos, what new revelations await us on distant worlds? Our author used artificial intelligence to enhance this article. Did you like it? 4.3/5 (26)
Yahoo
06-06-2025
- Science
- Yahoo
How one planet is revealing why it's so hard to detect life beyond Earth
Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more. A tiny sign revealed in April seemed like it might change the universe as we know it. Astronomers had detected just a hint, a glimmer of two molecules swirling in the atmosphere of a distant planet called K2-18b — molecules that on Earth are produced only by living things. It was a tantalizing prospect: the most promising evidence yet of an extraterrestrial biosignature, or traces of life linked to biological activity. But only weeks later, new findings suggest the search must continue. 'It was exciting, but it immediately raised several red flags because that claim of a potential biosignature would be historic, but also the significance or the strength of the statistical evidence seemed to be too high for the data,' said Dr. Luis Welbanks, a postdoctoral research scholar at Arizona State University's School of Earth and Space Exploration. While the molecules identified on K2-18b by the April study — dimethyl sulfide, or DMS, and dimethyl disulfide, or DMDS — are associated largely with microbial organisms on our planet, scientists point out that the compounds can also form without the presence of life. Now, three teams of astronomers not involved with the research, including Welbanks, have assessed the models and data used in the original biosignature discovery and got very different results, which they have submitted for peer review. Meanwhile, the lead author of the April study, Nikku Madhusudhan, and his colleagues have conducted additional research that they say reinforces their previous finding about the planet. And it's likely that additional observations and research from multiple groups of scientists are on the horizon. The succession of research papers revolving around K2-18b offers a glimpse of the scientific process unfolding in real time. It's a window into the complexities and nuances of how researchers search for evidence of life beyond Earth — and shows why the burden of proof is so high and difficult to reach. Located 124 light-years from Earth, K2-18b is generally considered a worthy target to scour for signs of life. It is thought to be a Hycean world, a planet entirely covered in liquid water with a hydrogen-rich atmosphere, according to previous research led by Madhusudhan, a professor of astrophysics and exoplanetary science at the University of Cambridge's Institute of Astronomy. And as such, K2-18b has rapidly attracted attention as a potentially habitable place beyond our solar system. Convinced of K2-18b's promise, Madhusudhan and his Cambridge colleagues used observations of the planet by the largest space telescope in operation, the James Webb Space Telescope, to study the planet further. But two scientists at the University of Chicago — Dr. Rafael Luque, a postdoctoral scholar in the university's department of astronomy and astrophysics, and Michael Zhang, a 51 Pegasi b / Burbidge postdoctoral fellow — spotted some problems with what they found. After reviewing Madhusudhan and his team's April paper, which followed up on their 2023 research, Luque and Zhang noticed that the Webb data looked 'noisy,' Luque said. Noise, caused by imperfections in the telescope and the rate at which different particles of light reach the telescope, is just one challenge astronomers face when they study distant exoplanets. Noise can distort observations and introduce uncertainties into the data, Zhang said. Trying to detect specific gases in distant exoplanet atmospheres introduces even more uncertainty. The most noticeable features from a gas like dimethyl sulfide stem from a bond of hydrogen and carbon molecules — a connection that can stretch and bend and absorb light at different wavelengths, making it hard to definitively detect one kind of molecule, Zhang said. 'The problem is basically every organic molecule has a carbon-hydrogen bond,' Zhang said. 'There's hundreds of millions of those molecules, and so these features are not unique. If you have perfect data, you can probably distinguish between different molecules. But if you don't have perfect data, a lot of molecules, especially organic molecules, look very similar, especially in the near-infrared.' Delving further into the paper, Luque and Zhang also noticed that the perceived temperature of the planet appeared to increase sharply from a range of about 250 Kelvin to 300 Kelvin (-9.67 F to 80.33 F or -23.15 C to 26.85 C) in research Madhusudhan published in 2023 to 422 Kelvin (299.93 F or 148.85 C) in the April study. Such harsh temperatures could change the way astronomers think about the planet's potential habitability, Zhang said, especially because cooler temperatures persist in the top of the atmosphere — the area that Webb can detect — and the surface or ocean below would likely have even higher temperatures. 'This is just an inference only from the atmosphere, but it would certainly affect how we think about the planet in general,' Luque said. Part of the issue, he said, is that the April analysis didn't include data collected from all three Webb instruments Madhusudhan's team used over the past few years. So Luque, Zhang and their colleagues conducted a study combining all the available data to see whether they could achieve the same results, or even find a higher amount of dimethyl sulfide. They found 'insufficient evidence' of both molecules in the planet's atmosphere. Instead, Luque and Zhang's team spotted other molecules, like ethane, that could fit the same profile. But ethane does not signify life. Arizona State's Welbanks and his colleagues, including Dr. Matt Nixon, a postdoctoral researcher in the department of astronomy at the University of Maryland College Park, also found what they consider a fundamental problem with the April paper on K2-18b. The concern, Welbanks said, was with how Madhusudhan and his team created models to show which molecules might be in the planet's atmosphere. 'Each (molecule) is tested one at a time against the same minimal baseline, meaning every single model has an artificial advantage: It is the only explanation permitted,' Welbanks said. When Welbanks and his team conducted their own analysis, they expanded the model from Madhusudhan's study. '(Madhusudhan and his colleagues) didn't allow for any other chemical species that could potentially be producing these small signals or observations,' Nixon said. 'So the main thing we wanted to do was assess whether other chemical species could provide an adequate fit to the data.' When the model was expanded, the evidence for dimethyl sulfide or dimethyl disulfide 'just disappears,' Welbanks said. Madhusudhan believes the studies that have come out after his April paper are 'very encouraging' and 'enabling a healthy discussion on the interpretation of our data on K2-18b.' He reviewed Luque and Zhang's work and agreed that their findings don't show a 'strong detection for DMS or DMDS.' When Madhusudhan's team published the paper in April, he said the observations reached the three-sigma level of significance, or a 0.3% probability that the detections occurred by chance. For a scientific discovery that is highly unlikely to have occurred by chance, the observations must meet a five-sigma threshold, or below a 0.00006% probability that the observations occurred by chance. Meeting such a threshold will require many steps, Welbanks said, including repeated detections of the same molecule using multiple telescopes and ruling out potential nonbiological sources. While such evidence could be found in our lifetime, it is less likely to be a eureka moment and more a slow build requiring a consensus among astronomers, physicists, biologists and chemists. 'We have never reached that level of evidence in any of our studies,' Madhusudhan wrote in an email. 'We have only found evidence at or below 3-sigma in our two previous studies (Madhusudhan et al. 2023 and 2025). We refer to this as moderate evidence or hints but not a strong detection. I agree with (Luque and Zhang's) claim which is consistent with our study and we have discussed the need for stronger evidence extensively in our study and communications.' In response to the research conducted by Welbanks' team, Madhusudhan and his Cambridge colleagues have authored another manuscript expanding the search on K2-18b to include 650 types of molecules. They have submitted the new analysis for peer review. 'This is the largest search for chemical signatures in an exoplanet to date, using all the available data for K2-18b and searching through 650 molecules,' Madhusudhan said. 'We find that DMS continues to be a promising candidate molecule in this planet, though more observations are required for a firm detection as we have noted in our previous studies.' Welbanks and Nixon were pleased that Madhusudhan and his colleagues addressed the concerns raised but feel that the new paper effectively walks back central claims made in the original April study, Welbanks said. 'The new paper tacitly concedes that the DMS/DMDS detection was not robust, yet still relies on the same flawed statistical framework and a selective reading of its own results,' Welbanks said in an email. 'While the tone is more cautious (sometimes), the methodology continues to obscure the true level of uncertainty. The statistical significance claimed in earlier work was the product of arbitrary modeling decisions that are not acknowledged.' Luque said the Cambridge team's new paper is a step in the right direction because it explores other possible chemical biosignatures. 'But I think it fell short in the scope,' Luque said. 'I think it restricted itself too much into being a rebuttal to the (Welbanks) paper.' Separately, however, the astronomers studying K2-18b agree that pushing forward on researching the exoplanet contributes to the scientific process. 'I think it's just a good, healthy scientific discourse to talk about what is going on with this planet,' Welbanks said. 'Regardless of what any single author group says right now, we don't have a silver bullet. But that is exactly why this is exciting, because we know that we're the closest we have ever been (to finding a biosignature), and I think we may get it within our lifetime, but right now, we're not there. That is not a failure. We're testing bold ideas.'
