Scientists say they have found the strongest sign yet of possible life beyond the solar system after detecting chemical compounds on a distant exoplanet that on Earth are produced almost exclusively by living organisms.
Using the James Webb Space Telescope, researchers identified traces of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the atmosphere of K2-18b, a planet 124 light-years from Earth and roughly two-and-a-half times the size of our planet. The telescope can analyse the composition of the planet’s atmosphere by studying the light that passes through it from its small red sun.
On Earth, DMS and DMDS are primarily generated by microbial life, such as marine phytoplankton. While scientists caution that unknown chemical processes could produce the molecules, their presence on K2-18b, which lies within its star’s habitable zone, is seen as a potential indicator of life.
Professor Nikku Madhusudhan of Cambridge University’s Institute of Astronomy said: “This is the strongest evidence yet there is possibly life out there. I can realistically say that we can confirm this signal within one to two years. The amount we estimate of this gas in the atmosphere is thousands of times higher than what we have on Earth. So, if the association with life is real, then this planet will be teeming with life.”
The findings have led some researchers to speculate that K2-18b could even be covered with an ocean. Dr David Clements, an astrophysicist at Imperial College London who was not involved in the study, urged caution, noting that “while it does not yet represent a clear detection of Dimethyl Sulfide and Dimethyl Disulfide, it is a step in the right direction.”
Earlier this year, other analyses of Webb data using different statistical models found no strong evidence for DMS or DMDS. Madhusudhan’s team later reanalysed the data and reported being “more confident” that DMS best explains the observations. Meanwhile, Dr Renyu Hu at the California Institute of Technology and colleagues found that while some models including DMS fit the data slightly better, the results did not meet the statistical threshold required for a definitive detection.
The discovery has sparked excitement in the scientific community, highlighting both the potential for life on exoplanets and the challenges of confirming such findings.