Latest news with #K2-18b
NDTV
4 days ago
- Science
- NDTV
Is There Life Present On K2-18b Exoplanet? New Observations Provide Insights
A team of scientists claimed in April that a planet orbiting a distant star bore a possible signature of life, but the latest observations suggest otherwise. At the University of Cambridge, Nikku Madhusudhan and his colleagues claimed in April that they found hints of the molecules dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) in the atmosphere on K2-18b using the James Webb Space Telescope (JWST) data. On Earth, these sulfur-based compounds are primarily produced by marine microorganisms. Madhusudhan said those were the "first hints we are seeing of an alien world that is possibly inhabited". K2-18b is a super-Earth located 124 light-years away in the constellation Leo. It is approximately 2.6 times the diameter and 8.6 times the mass of Earth, orbiting a cool red dwarf star within the habitable zone. What did the other researchers say? Other researchers also analysed the same data using different statistical models and didn't find evidence for the presence of these molecules. Renyu Hu at the California Institute of Technology and his colleagues teamed up with Madhusudhan and his group to analyse the observations of K2-18b. "The paper does not provide conclusive evidence for the existence of this molecule in the atmosphere," Hu said as quoted by the New Scientist. The second team found no statistical evidence.. However, Madhusudhan told New Scientist that his colleagues analysed the data again, which made him "more confident" that DMS was the best explanation. James Webb's near-infrared camera was used by the second group of researchers to look at the light coming from K2-18b's star. It can reveal what molecules exist in the atmosphere after passing through the planet's atmosphere. The camera looked at a different wavelength of light compared to the mid-infrared measurements that were used for the analysis done in April. "This model dependency just speaks to the fact that it is a very weak signal, if there is any signal at all," Hu said. "I would just exercise caution". "This paper is very clear in saying that there is no evidence for dimethyl sulphide. There is no statistical evidence for any of these gases," Luis Welbanks at Arizona State University said as quoted. "We seem to be coming to the end of the debate on whether DMS is present in detectable levels in the [K2-18b] atmosphere, as the increased precision has not helped to detect it at a higher significance," Jake Taylor at the University of Oxford said, as quoted. Scientists previously proposed that K2-18b could be a "Hycean world," a planet with a hydrogen-rich atmosphere and vast ocean, making it a prime candidate for hosting life. Hu and his team found that for certain hydrogen-rich atmospheres, chemicals can produce DMS without the presence of life. "A key takeaway is that biosignatures are going to be hard, no matter what kind of planet we are talking about," Jacob Bean, an astronomer at the University of Chicago, who was not involved in the study, said as quoted by The New York Times. All researchers, however, agreed that the planet is rich in water. Strong evidence for the presence of methane and carbon dioxide was also found by Hu and his team. It implies the existence of water, Hu said. However, additional studies could provide insights into the planet's atmospheric composition, temperature profile and potential biosignatures.
New York Times
24-07-2025
- Science
- New York Times
Hints of Life on Exoplanet Recede Even Further
In April, a team of scientists based at the University of Cambridge claimed that a planet orbiting a distant star bore a possible signature of life. The announcement kicked up a fierce debate among astronomers, with many skeptics arguing that the evidence was too ambiguous. Now a NASA-led team has made a new set of observations of the planet known as K2-18b, which lies 124 light-years from Earth. They have provided a clearer picture of the planet — confirming the presence of water, perhaps even as a liquid ocean. But the new observations have failed to confirm evidence for life. In the original study, the Cambridge team claimed that K2-18b appeared to have a gas in its atmosphere that on Earth is produced only by living things. The NASA study did not find strong evidence for that gas. What's more, the NASA team argues that even if the gas was on K2-18b, it might have formed through mere chemistry. What once seemed like a promising clue of life — a biosignature — might be a mirage. 'A key takeaway is that biosignatures are going to be hard, no matter what kind of planet we are talking about,' said Jacob Bean, an astronomer at Cornell University, who was not involved in the study. The NASA team, working with the leader of the Cambridge group, posted its new results online last week. The scientists have submitted the study to a scientific journal for publication. Want all of The Times? Subscribe.
Yahoo
29-06-2025
- Science
- Yahoo
Is the bar higher for scientific claims of alien life?
When you buy through links on our articles, Future and its syndication partners may earn a commission. The search for extraterrestrial life has long gone back and forth between scientific curiosity, public fascination and outright skepticism. Recently, scientists claimed the 'strongest evidence' of life on a distant exoplanet – a world outside our solar system. Grandiose headlines often promise proof that we are not alone, but scientists remain cautious. Is this caution unique to the field of astrobiology? In truth, major scientific breakthroughs are rarely accepted quickly. Newton's laws of motion and gravity, Wegener's theory of plate tectonics, and human-made climate change all faced prolonged scrutiny before achieving consensus. But does the nature of the search for extraterrestrial life mean that extraordinary claims require even more extraordinary evidence? We've seen groundbreaking evidence in this search beforehand, from claims of biosignatures (potential signs of life) in Venus's atmosphere to NASA rovers finding 'leopard spots' – a potential sign of past microbial activity – in a Martian rock. Both stories generated a public buzz around the idea that we might be one step closer to finding alien life. But on further inspection, abiotic (non-biological) processes or false detection became more likely explanations. In the case of the exoplanet, K2-18 b, scientists working with data from the James Webb Space Telescope (JWST) announced the detection of gases in the planet's atmosphere – methane, carbon dioxide, and more importantly, two compounds called dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). As far as we know, on Earth, DMS/DMDS are produced exclusively by living organisms. Their presence, if accurately confirmed in abundance, would suggest microbial life. The researchers even suggest there's a 99.4% probability that the detection of these compounds wasn't a fluke – a figure that, with repeat observations, could reach the gold standard for statistical certainty in the sciences. This is a figure known as five sigma, which equates to about a one in a million chance that the findings are a fluke. So why hasn't the scientific community declared this the discovery of alien life? The answer lies in the difference between detection and attribution, and in the nature of evidence itself. JWST doesn't directly 'see' molecules. Instead, it measures the way that light passes through or bounces off a planet's atmosphere. Different molecules absorb light in different ways, and by analysing these absorption patterns – called spectra – scientists infer what chemicals are likely to be present. This is an impressive and sophisticated method – but also an imperfect one. It relies on complex models that assume we understand the biological reactions and atmospheric conditions of a planet 120 light years away. The spectra suggesting the existence of DMS/DMDS may be detected because you cannot explain the spectrum without the molecule you've predicted, but it could also result from an undiscovered or misunderstood molecule instead. Given how momentous the conclusive discovery of extraterrestrial life would be, these assumptions mean that many scientists err on the side of caution. But is this the same for other kinds of science? Let's compare with another scientific breakthrough: the detection and attribution of human-made climate change. The relationship between temperature and increases in CO₂ was first observed by the Swedish scientist Svante Arrhenius in 1927. It was only taken seriously once we began to routinely measure temperature increases. But our atmosphere has many processes that feed CO₂ in and out, many of which are natural. So the relationship between atmospheric CO₂ and temperature may have been validated, but the attribution still needed to follow. Carbon has three so-called flavors, known as isotopes. One of these isotopes, carbon-14, is radioactive and decays slowly. When scientists observed an increase in atmospheric carbon dioxide but a low volume of carbon-14, they could deduce that the carbon was very old – too old to have any carbon-14. Fossil fuels – coal, oil and natural gas – are composed of ancient carbon and thus are devoid of carbon-14. So the attribution of anthropogenic climate change was proven beyond reasonable doubt, with 97% acceptance among scientists. In the search for extraterrestrial life, much like climate change, there is a detection and attribution phase, which requires the robust testing of hypotheses and also rigorous scrutiny. In the case of climate change, we had in situ observations from many sources. This means roughly that we could observe these sources close up. The search for extraterrestrial life relies on repeated observations from the same sensors that are far away. In such situations, systematic errors are more costly. Further to this, both the chemistry of atmospheric climate change and fossil fuel emissions were validated with atmospheric tests under lab conditions from 1927 onwards. Much of the data we see touted as evidence for extraterrestrial life comes from light years away, via one instrument, and without any in situ samples. The search for extraterrestrial life is not held to a higher standard of scientific rigor but it is constrained by an inability to independently detect and attribute multiple lines of evidence. For now, the claims about K2-18 b remain compelling but inconclusive. That doesn't mean we aren't making progress. Each new observation adds to a growing body of knowledge about the universe and our place in it. The search continues – not because we're too cautious, but because we are rightly so. This article is republished from The Conversation under a Creative Commons license. Read the original article.
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.'
