Researchers estimate that an additional 16 to 24 hours of JWST observations could provide the data needed to reach this five-sigma benchmark.
Photo: Artist concept of an exoplanet K2-18 b/Source: NASA
New findings from NASA’s James Webb Space Telescope (JWST) have provided compelling evidence that the exoplanet K2-18b may contain atmospheric molecules that, on Earth, are exclusively produced by living organisms.
Astronomers, led by researchers at the University of Cambridge, analyzed data from the JWST and identified the possible presence of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) in K2-18b’s atmosphere, which orbits its star in the habitable zone.
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On Earth, these molecules—DMS and DMDS—are typically produced by microbial life, especially marine phytoplankton. Although there could be an unknown chemical process responsible for their formation on K2-18b, this discovery marks the most compelling evidence to date suggesting that life might exist beyond our solar system.
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As per earlier observations made in 2023 with NASA’s James Webb Space Telescope into K2-18 b revealed–it is an exoplanet 8.6 times as massive as Earth. The findings have revealed the presence of carbon-bearing molecules including methane and carbon dioxide. Webb’s discovery added to recent studies suggesting that K2-18 b could be a Hycean exoplanet–one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface.
Initial hints of dimethyl sulfide (DMS) in K2-18b’s atmosphere were based on data from JWST’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph), which operate in the near-infrared range (0.8–5 microns). In contrast, the latest, independent detection came about using JWST’s MIRI (Mid-Infrared Instrument), which observes in the mid-infrared spectrum (6–12 microns).
Crucially, this new data reached a statistical confidence level of three-sigma, indicating there’s just a 0.3% chance the signal occurred randomly. However, for a finding to meet the standard for a confirmed scientific discovery, it must surpass the five-sigma threshold—corresponding to a less than 0.00006% probability of being a fluke.
Researchers estimate that an additional 16 to 24 hours of JWST observations could provide the data needed to reach this five-sigma benchmark.
“It’s important that we’re deeply skeptical of our own results, because it’s only by testing and testing again that we will be able to reach the point where we’re confident in them,” Professor Nikku Madhusudhan of the University of Cambridge, U.K. said. “That’s how science has to work”, he said.
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