Astronomers have detected what they describe as the strongest evidence yet for life beyond our solar system, after the James Webb Space Telescope spotted potential chemical signatures of biological activity on a planet 124 light years away.
The planet, K2-18 b, orbits a red dwarf star in the constellation Leo. Observations revealed traces of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), compounds that on Earth are produced almost exclusively by living organisms, particularly marine phytoplankton.
Professor Nikku Madhusudhan of the University of Cambridge, who led the research, said the findings could mark a turning point in the search for extraterrestrial life. “Decades from now, we may look back at this point in time and recognise it was when the living universe came within reach,” he said.
The results, published in The Astrophysical Journal Letters, show the molecules at concentrations thousands of times higher than on Earth. However, the detection has a statistical significance of three sigma, meaning a 0.3% chance of occurring by random chance, which falls short of the usual gold standard for discoveries.
Some scientists urge caution. Dr Nora Hänni of the University of Berne noted that DMS has been found on lifeless comets, and other non-biological processes could explain the signals. The nature of K2-18 b itself is debated: while Madhusudhan’s team suggests it is a water world, others argue it could be a gas planet or have magma oceans.
Despite the uncertainty, Madhusudhan maintains that no known abiotic process can account for the observations. “This is the strongest evidence to date for a biological activity beyond the solar system,” he said.
