Latest news with #LuisWelbanks
Observer
5 days ago
- Science
- Observer
New studies dismiss signs of life on distant planet
In April, a team of astronomers announced that they might — just might — have found signs of life on a planet over 120 light-years from Earth. The mere possibility of extraterrestrial life was enough to attract attention worldwide. It also attracted intense scrutiny from other astronomers. Over the past month, researchers have independently analyzed the data, which suggested that the planet, called K2-18b, has a molecule in its atmosphere that could have been created by living organisms. Three different analyses have all reached the same conclusion: They see no compelling evidence for life on K2-18b. 'The claim just absolutely vanishes,' said Luis Welbanks, an astronomer at Arizona State University and an author of one of the studies. The debate has less to do with the existence of alien life than with the challenge of observing distant planets. We can see a nearby planet like Jupiter because it reflects enough sunlight to become visible to the naked eye. But a planet like K2-18b is so far away that it becomes invisible not just to the naked eye but to conventional telescopes. Astronomers have devised a series of increasingly sophisticated tricks to glean information about distant planets. They can measure the wobble of stars and the gravity of planets orbiting them. In 2010, researchers caught a glimpse of GJ 1214b, a planet 48 light-years away, as it passed in front of the star it orbits. When the star's light shone through the planet's atmosphere, certain wavelengths were absorbed, indicating that GJ 1214b might have an atmosphere rich in water vapor. In 2022, astronomers began using a powerful new tool to peer at distant planets in this way. They pointed the James Webb Space Telescope at faraway solar systems and began detecting exquisitely faint patterns in starlight, clues to the complexity of exoplanet atmospheres. The following year, Nikku Madhusudhan, an astronomer at the University of Cambridge, and his colleagues zeroed in on K2-18b as it passed in front of its star, using instruments on the Webb telescope that are extremely sensitive to near-infrared light. As K2-18b passed in front of the star, the starlight underwent a subtle shift, caused by a planetary atmosphere containing hydrogen, carbon dioxide, and methane, the researchers concluded. They also found suggestive hints of a fourth gas, dimethyl sulfide, which could be a very big deal. On Earth, the only source of dimethyl sulfide in the atmosphere is life. Photosynthetic microbes in the ocean produce the molecule as a defense against ultraviolet light from the sun. The molecule escapes their cells and ends up in the air. But the signal was so faint that it was hard to be certain that it was real. So Madhusudhan's team arranged to look again at K2-18b in 2024. This time, they used a different instrument on the space telescope, which looks at longer wavelengths of mid-infrared light. In the team's second search, they again found a signature of dimethyl sulfide, this one seemingly even stronger than the first. In April, Madhusudhan and his colleagues described their results in a paper published in the Astrophysical Journal Letters. Speaking at a news conference the day before, Madhusudhan said there was only 'a three-in-a-thousand chance of this being a fluke.' Rafael Luque, an astronomer at the University of Chicago, characterized Madhusudhan as a world expert on exoplanets. 'Madhu has been a pioneer in the field,' he said. 'I have the utmost respect for that team.' Nevertheless, Luque and his colleagues decided to take a look at the data for themselves. For their own analysis, the scientists combined all the observations of K2-18b in both the near-infrared and mid-infrared wavelengths. On May 19, they reported that this combined data contained strong signals of hydrogen, carbon dioxide and methane, but no clear evidence of dimethyl sulfide. The critics argue that the new mid-infrared observations were much weaker than those in the near-infrared. On its own, they say, the mid-infrared light could fool researchers with faint noise masquerading as a real signal of dimethyl sulfide. 'I can just say straight up there is no statistically significant signal in the data that was published a month ago,' Jacob Bean said. Bean, an astronomer at the University of Chicago who discovered GJ 1214b's atmosphere, worked with Luque on the May 19 study. Welbanks, a former student of Madhusudhan's, and his colleagues analyzed the K2-18b data differently. If the mid-infrared signal was genuine, did it have to come from dimethyl sulfide? The team considered 90 molecules that could plausibly be produced on a planet like K2-18b. Those molecules didn't have to be produced by life, however; chemical reactions driven by sunlight could be enough. The researchers concluded that the mid-infrared signal might have been produced by 59 of the 90 molecules. The strongest candidate in their analysis was not dimethyl sulfide but propyne, a gas that welders use as fuel. Welbanks and his colleagues aren't claiming that propyne is present on K2-18b. They simply argue that the faint light from the planet's atmosphere can create ambiguous patterns that might be the result of one of many gases. Such scant data certainly isn't sufficient to consider any planet to be a possible home for life. On May 15, Madhusudhan and his colleagues responded to Welbanks' team with a study of their own. They examined 650 possible molecules that might be in K2-18b's atmosphere; dimethyl sulfide ended up among the molecules at the top of the list. 'We're exactly where we left off a month ago; it's a good candidate,' Madhusudhan said. Welbanks said the new study by Madhusudhan simply provided more evidence that dimethyl sulfide does not stand out compared to other possible molecules on K2-18b. 'In effect, this is a self-rebuttal,' he said. It's possible that the debate over K2-18b could be resolved within months. Last year, Renyu Hu, an astronomer at the Jet Propulsion Laboratory, and his colleagues made more near-infrared observations of the planet. They are now preparing their results. 'It will include substantially more data than previously published,' Hu said. Bean said the new observations could dispel much of the confusion about K2-18b. 'The science is working,' he said. 'It's going to play out pretty quickly, and I think we'll have some clarity.' This article originally appeared in
Yahoo
7 days ago
- Science
- Yahoo
Doubts over hope of alien life on exoplanet K2-18b as case for biosignatures weakens
A growing number of studies have cast doubt on earlier claims about signs of life on K2-18b, a planet 124 light-years away in the Leo constellation, concluding that the available data doesn't support such bold interpretations. Last month, scientists had announced that they might have identified what appeared to be the most promising signs of alien life discerned so far on the distant planet. However, latest research contends that there was not enough evidence to estimate alien presence. K2-18b orbits within the habitable zone of its star, making it a compelling target for the search of alien life due to the potential presence of liquid water. Astronomers working with the James Webb Space Telescope drew global attention in April by reporting possible traces of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the planet's atmosphere. On Earth, these compounds are produced exclusively by living organisms such as marine algae, which is why they are considered potential biosignatures—chemical hints that life might exist elsewhere. Led by Cambridge University's Nikku Madhusudhan, the research team was careful to stress that the potential biosignature was far from conclusive. The signal reached a three-sigma level of statistical significance, meaning there remains a small but meaningful possibility that the result was a fluke. Two of Madhusudhan's former students, Luis Welbanks of Arizona State University and Matthew Nixon of the University of Maryland, were part of a team that re-examined the data behind the initial announcement. In a preprint study published online towards the end of last month, they reported that when using alternative statistical models, the signals originally interpreted as potential biosignatures no longer stand out. In one approach, the researchers broadened the pool of possible atmospheric chemicals from 20 to 90, significantly weakening the case for a unique biological explanation. Embracing the ongoing scientific discussion, Madhusudhan highlighted the importance of keeping an open mind throughout the research process. His team added to the conversation by releasing a new preprint study last week that expanded the list of potential atmospheric chemicals to 650. Among the top candidates identified as an indicator of alien life was dimethyl sulfide (DMS). Meanwhile, dimethyl disulfide (DMDS), which had featured prominently in their earlier announcement, was no longer considered a leading possibility. Astronomers observe distant exoplanets like K2-18b by tracking their passage across their host stars, which allows them to analyze how molecules in the planet's atmosphere absorb specific wavelengths of starlight. Earlier this week, a study led by postdoctoral researcher Rafael Luque at the University of Chicago combined Webb's observations of K2-18b in both near-infrared and mid-infrared wavelengths. The research found no statistically significant evidence for dimethyl sulfide (DMS) or dimethyl disulfide (DMDS). In addition, an earlier paper by Oxford astrophysicist Jake Taylor, using a basic statistical method, also reported no strong signs of biosignatures. However, Madhusudhan dismissed Taylor's paper noting the simple exercise used to draw conclusions was far from a robust method to observe physical phenomena. The scientist also highlighted that more data on K2-18b will be collected over the next year, which should help provide a clearer and more definitive picture.
Asharq Al-Awsat
24-05-2025
- Science
- Asharq Al-Awsat
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, emphasizing 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. 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-analyzed 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. 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". Telescopes observe such far-off exoplanets when they cross in front of their star, allowing astronomers to analyze 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.
New York Times
23-05-2025
- Science
- New York Times
New Studies Dismiss Signs of Life on Distant Planet
In April, a team of astronomers announced that they might — just might — have found signs of life on a planet over 120 light-years from Earth. The mere possibility of extraterrestrial life was enough to attract attention worldwide. It also attracted intense scrutiny from other astronomers. Over the past month, researchers have independently analyzed the data, which suggested that the planet, called K2-18b, has a molecule in its atmosphere that could have been created by living organisms. Three different analyses have all reached the same conclusion: They see no compelling evidence for life on K2-18b. 'The claim just absolutely vanishes,' said Luis Welbanks, an astronomer at Arizona State University and an author of one of the studies. The debate has less to do with the existence of alien life than with the challenge of observing distant planets. We can see a nearby planet like Jupiter because it reflects enough sunlight to become visible to the naked eye. But a planet like K2-18b is so far away that it becomes invisible not just to the naked eye but to conventional telescopes. Astronomers have devised a series of increasingly sophisticated tricks to glean information about distant planets. They can measure the wobble of stars and the gravity of planets orbiting them. In 2010, researchers caught a glimpse of GJ 1214b, a planet 48 light-years away, as it passed in front of the star it orbits. When the star's light shined through the planet's atmosphere, certain wavelengths were absorbed indicating that GJ 1214b might have an atmosphere rich in water vapor. In 2022, astronomers began using a powerful new tool to peer at distant planets this way. They pointed the James Webb Space Telescope at faraway solar systems and began detecting exquisitely faint patterns in starlight, clues to the complexity of exoplanet atmospheres. The following year, Nikku Madhusudhan, an astronomer at the University of Cambridge, and his colleagues zeroed in on K2-18b as it passed in front of its own star, using instruments on the Webb telescope that are exquisitely sensitive to near-infrared light. As K2-18b passed in front of the star, the starlight underwent a subtle shift — caused by a planetary atmosphere containing hydrogen, carbon dioxide and methane, the researchers concluded. They also found suggestive hints of a fourth gas, dimethyl sulfide — which could be a very big deal. On Earth, the only source for dimethyl sulfide in the atmosphere is life. Photosynthetic microbes in the ocean produce the molecule as a defense against ultraviolet light from the sun. The molecule escapes their cells and ends up in the air. But the signal was so faint that it was hard to be certain that it was real. So Dr. Madhusudhan's team arranged to look again at K2-18b, in 2024. This time, they used a different instrument on the space telescope, which looks at longer wavelengths of mid-infrared light. In the team's second search, they again found a signature of dimethyl sulfide, this one seemingly even stronger than the first. In April, Dr. Madhusudhan and his colleagues described their results in a paper published in Astrophysical Journal Letters. Speaking at a news conference the day before, Dr. Madhusudhan said there was only 'a three-in-a-thousand chance of this being a fluke.' Rafael Luque, an astronomer at the University of Chicago, characterized Dr. Madhusudhan as a world expert on exoplanets. 'Madhu has been a pioneer in the field,' he said. 'I have the utmost respect for that team.' Nevertheless, Dr. Luque and his colleagues decided to take a look at the data for themselves. For their own analysis, the scientists combined all the observations of K2-18b in both the near-infrared and mid-infrared wavelengths. On Monday, they reported that this combined data contained strong signals of hydrogen, carbon dioxide and methane, but no clear evidence of dimethyl sulfide. The critics argue that the new mid-infrared observations were much weaker than those in near-infrared. On its own, they say, the mid-infrared light could fool researchers with faint noise masquerading as a real signal of dimethyl sulfide. 'I can just say straight up there is no statistically significant signal in the data that were published a month ago,' said Jacob Bean. Dr. Bean, an astronomer at the University of Chicago who discovered GJ 1214b's atmosphere, worked with Dr. Luque on Monday's study. Dr. Welbanks, a former student of Dr. Madhusudhan's, and his colleagues analyzed the K2-18b data in a different way. If the mid-infrared signal was genuine, did it have to come from dimethyl sulfide? The team considered 90 different molecules that could plausibly be produced on a planet like K2-18b. Those molecules didn't have to be produced by life, however; chemical reactions driven by sunlight could be enough. The researchers concluded that the mid-infrared signal might have been produced by 59 of the 90 molecules. The strongest candidate in their analysis was not dimethyl sulfide but propyne, a gas that welders use as fuel. Dr. Welbanks and his colleagues aren't claiming that propyne is actually present on K2-18b. They simply argue that the faint light from the planet's atmosphere can create ambiguous patterns that might be the result of one of many gases. Such scanty data certainly isn't sufficient to consider any planet to be a possible home for life. Last week, Dr. Madhusudhan and his colleagues responded to Dr. Welbanks's team with a study of their own. They examined 650 possible molecules that might be in K2-18b's atmosphere; dimethyl sulfide ended up among the molecules at the top of the list. 'We're exactly where we left off a month ago; it's a good candidate,' Dr. Madhusudhan said. Dr. Welbanks said that the new study by Dr. Madhusudhan simply provided more evidence that dimethyl sulfide does not stand out compared to other possible molecules on K2-18b. 'In effect, this is a self-rebuttal,' he said. It's possible that the debate over K2-18b could be resolved within months. Last year Renyu Hu, an astronomer at the Jet Propulsion Laboratory, and his colleagues made more near-infrared observations of the planet. They are now preparing their results. 'It will include substantially more data than previously published,' Dr. Hu said. Dr. Bean said that the new observations could dispel much of the confusion about K2-18b. 'The science is definitely working,' he said. 'It's going to play out pretty quickly, and I think we'll have some clarity.'
