{"id":795406,"date":"2025-04-17T21:29:03","date_gmt":"2025-04-18T02:29:03","guid":{"rendered":"https:\/\/spaceweekly.com\/?p=795406"},"modified":"2025-04-17T21:29:03","modified_gmt":"2025-04-18T02:29:03","slug":"life-on-k2-18b-exciting-new-results-met-with-skepticism","status":"publish","type":"post","link":"https:\/\/spaceweekly.com\/?p=795406","title":{"rendered":"Life on K2-18b? Exciting new results met with skepticism"},"content":{"rendered":"
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\nView larger. | Artist\u2019s concept of K2-18b as a Hycean world with a global ocean and hydrogen atmosphere. Could there be life on K2-18b? The new results from the Webb space telescope are tantalizing but not yet conclusive. And they\u2019ve been met with skepticism from other scientists. Image via A. Smith\/ N. Madhusudhan (University of Cambridge).<\/figcaption><\/figure>\n
K2-18b is an exoplanet 124 light-years away and is larger and more massive than Earth.<\/strong> Scientists said it might have a deep global ocean under a hydrogen atmosphere. Could it support life?<\/li>\n
New observations from the Webb space telescope<\/strong> show there is a molecule called dimethyl sulfide in its atmosphere, a possible signature of life. Webb had previously tentatively detected it before, but the new observations show a stronger signal.<\/li>\n
The results don\u2019t prove there is life on K2-18b,<\/strong> but they are tantalizing. Other scientists are quite skeptical, however.<\/li>\n<\/ul>\n
Life on exoplanet K2-18b?<\/h3>\n
In 2023, scientists announced they had tentatively identified the gas dimethyl sulfide \u2013 a possible<\/em> biosignature of life \u2013 in the atmosphere of K2-18b, an exoplanet 124 light-years away. On April 17, 2025, scientists at the University of Cambridge in the U.K. said they found the gas again with the Webb space telescope, but this time with a stronger signal. They said the amount of dimethyl sulfide appears to be thousands of times more abundant on K2-18b than on Earth. However, more data is needed to fully confirm its presence and whether it is connected to life \u2026 or not. And many scientists are still skeptical.<\/p>\n
The New York Times<\/em> first broke the news on April 16, 2025.<\/p>\n
The researchers published their peer-reviewed results in The Astrophysical Journal Letters<\/em> on April 17, 2025.<\/p>\n
A hint of dimethyl sulfide<\/h3>\n
K2-18b is a super-Earth or sub-Neptune world, orbiting in the habitable zone \u2013 where liquid water could exist \u2013 of its star. Its exact classification is also still a matter of debate among scientists, which has a lot of bearing on the reported discovery. It\u2019s about 8.6 times as massive and 2.6 times larger than Earth, and orbits a red dwarf star about 124 light-years away.<\/p>\n
When scientists announced the possible detection of dimethyl sulfide<\/em> (DMS) in September 2023, using the Webb space telescope, the news spurred much debate. It was a potentially exciting discovery, to be sure. The gas is a potential biosignature, a chemical, molecular or other trace of biological life. But the detection was weak and far from conclusive. Astronomers would need to observe the planet again with Webb to try to determine if the gas really was there or not.<\/p>\n
Nikku Madhusudhan, a University of Cambridge astrophysicist, was involved in the previous research and is the lead author of the paper about the latest findings. He said:<\/p>\n
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We didn\u2019t know for sure whether the signal we saw last time was due to dimethyl sulfide, but just the hint of it was exciting enough for us to have another look with Webb using a different instrument.<\/p>\n<\/blockquote>\n
Webb had also previously found methane and carbon dioxide in the atmosphere of K2-18b. Those signals were much stronger, however, and considered to be confirmed. The dimethyl sulfide signal was a lot weaker, or of \u201clow statistical significance,\u201d in more scientific terms.<\/p>\nNikku Madhusudhan at the University of Cambridge in the U.K. led the new study about K2-18b. Image via Atlantic Studios\/ University of Cambridge.<\/figcaption><\/figure>\n
New observations with Webb<\/h3>\n
For the older initial observations, Webb used its Near-Infrared Imager and Slitless Spectrograph (NIRISS) and Near-Infrared Spectrograph (NIRSpec) instruments. But for the new observations, Webb used its Mid-Infrared Instrument (MIRI) instead. Madhusudhan said:<\/p>\n
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This is an independent line of evidence, using a different instrument than we did before and a different wavelength range of light, where there is no overlap with the previous observations. The signal came through strong and clear.<\/p>\n<\/blockquote>\n
Co-author M\u00e5ns Holmberg at the Space Telescope Science Institute in Baltimore, Maryland, added:<\/p>\n
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It was an incredible realization seeing the results emerge and remain consistent throughout the extensive independent analyses and robustness tests.<\/p>\n<\/blockquote>\n
Madhusudhan also discussed the new findings in a livestream that you can replay and watch here:<\/p>\n
![\"Smiling](\"https:\/\/earthsky.org\/upl\/2025\/04\/Nikku-Madhusudhan-Atlantic-Studios-University-of-Cambridge.jpg\")
![\"Graph](\"https:\/\/earthsky.org\/upl\/2025\/04\/graph-transmission-spectrum-K2-18b-dimethyl-sulfide-dimethyl-disulfide-University-of-Cambridge-April-17-2025.jpg\")