Are we alone? Fingerprints of alien life discovered in distant planet atmosphere 

Astronomers, led by the University of Cambridge, have used data from the James Webb Space Telescope (JWST) to detect the fingerprints of alien life in the atmosphere of a distant planet.  

Scientists from the university confirmed on April 17, 2025, that possible signs of life were found around the exoplanet K2-18b, which lies 124 light years away in the constellation of Leo. 

Specifically, signs of the chemical dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) were found which on Earth are only produced by life, primarily microbial life such as marine phytoplankton. 

Cambridge University said that this was the “first time that carbon-based molecules were discovered in the atmosphere of an exoplanet in the habitable zone”. 

The results have excited scientists as they were consistent with predictions for a ‘Hycean’ planet which is defined as a “habitable ocean-covered world underneath a hydrogen-rich atmosphere”. 

BEST-BACKGROUNDS / Shutterstock.comThe observations have reached the ‘three-sigma’ level of statistical significance – meaning there is a 0.3% probability that they occurred by chance.  

However, to reach the accepted classification for scientific discovery, the observations would have to cross the five-sigma threshold, meaning there would be below a 0.00006% probability they occurred by chance. 

“We didn’t know for sure whether the signal we saw last time was due to DMS, but just the hint of it was exciting enough for us to have another look with JWST using a different instrument,” said Professor Nikku Madhusudhan from Cambridge’s Institute of Astronomy, who led the research. 

Scientists used the telescope’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) instruments to detect the inference of DMS. 

“Earlier theoretical work had predicted that high levels of sulfur-based gases like DMS and DMDS are possible on Hycean worlds. And now we’ve observed it, in line with what was predicted. Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have,” said Madhusudhan. 

While the university is not yet claiming a definitive discovery and the presence of DMS could be for previously unknown reasons, scientists believe that “humanity is taking new steps toward answering that most essential of questions: are we alone?”. 

“Decades from now, we may look back at this point in time and recognize it was when the living universe came within reach. This could be the tipping point, where suddenly the fundamental question of whether we’re alone in the universe is one we’re capable of answering,” said Madhusudhan.  

The James Webb Space Telescope is a collaboration between NASA, ESA and the Canadian Space Agency (CSA).

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