Scientists have uncovered what they describe as the most compelling evidence to date suggesting the existence of life beyond our solar system. A team led by researchers from Cambridge University has detected chemical signatures in the atmosphere of exoplanet K2-18b that, on Earth, are exclusively produced by living organisms.
Using the James Webb Space Telescope (JWST), astronomers identified the presence of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) in the planet’s atmosphere. These compounds are particularly significant because on our planet, they are only generated by biological processes, primarily by marine phytoplankton and bacteria.
“This is the strongest evidence yet that there is possibly life out there,” said Professor Nikku Madhusudhan, the study’s lead author from Cambridge’s Institute of Astronomy. “I can realistically say that we can confirm this signal within one to two years.”
What Makes This Discovery Significant
K2-18b, located approximately 124 light-years away in the constellation Leo, is about 2.6 times larger than Earth and 8.6 times more massive. The planet orbits within the habitable zone of its red dwarf star, meaning liquid water could potentially exist on its surface—a crucial ingredient for life as we know it.
The observations have reached what scientists call a “three-sigma” level of statistical significance, indicating there is only a 0.3% probability that these findings occurred by chance. However, to be classified as a definitive scientific discovery, the observations would need to reach a five-sigma threshold, representing less than a 0.00006% probability of being coincidental.
What’s particularly striking about the discovery is the concentration of these potential biosignature gases. Researchers calculate that the possible concentrations of DMS and DMDS on K2-18b appear to be over 10 parts per million, thousands of times higher than levels found in Earth’s atmosphere. If confirmed, this could suggest the planet is teeming with microbial life.
“This is a transformational moment in the search for life beyond the solar system,” Madhusudhan stated. “We have entered the era of observational astrobiology.”
Cautious Optimism in the Scientific Community
Despite the excitement, both the research team and external scientists emphasise the need for caution. The researchers are not claiming to have definitively discovered alien life but rather a possible biosignature that requires further investigation.
“It’s in no one’s interest to claim prematurely we have detected life,” Madhusudhan noted during a recent news conference, though he suggested that the most plausible interpretation of their findings is that K2-18b possesses a warm ocean abundant with life.
Other astronomers have expressed enthusiasm about this initial step in understanding K2-18b, but remain hesitant to make sweeping claims. The research team estimates that between 16 and 24 additional hours of observation time with the JWST may help them reach the five-sigma significance level needed for scientific consensus.