In April 2025, scientists announced what may be the strongest evidence yet of possible life beyond Earth. A team led by Nikku Madhusudhan from the University of Cambridge discovered chemical traces in the atmosphere of exoplanet K2-18b that could point to biological activity.
Using the powerful James Webb Space Telescope (JWST), the researchers detected dimethyl sulfide (DMS) and possibly dimethyl disulfide (DMDS)—gases that, on Earth, are mostly produced by tiny marine life such as plankton.
The findings, published in The Astrophysical Journal Letters, show a three-sigma confidence level, meaning there’s only a 0.3% chance the signal is a fluke. While promising, this still falls short of the five-sigma standard needed for scientific certainty.
K2-18b, discovered by NASA’s Kepler mission in 2015, is located 124 light-years away in the Leo constellation. It’s about 8.6 times the mass of Earth and lies in the star’s habitable zone, where temperatures could allow for liquid water. The planet may be a Hycean world—a type of ocean-covered planet with a hydrogen-rich atmosphere.
Earlier observations in 2023 had already found methane and carbon dioxide, sparking hopes that the planet might support life. The new 2025 data shows stronger signs of DMS/DMDS, with amounts far higher than what’s seen on Earth.
Still, not all scientists agree. A 2024 study found no clear signs of DMS in earlier data. Some experts say the chemicals could also come from non-living sources, like volcanoes or comets. Ryan MacDonald of the University of Michigan warned that the signal is not yet strong enough to confirm anything.
Researchers say 16–24 more hours of JWST time could give a more definite answer within a year or two. Until then, K2-18b remains one of the best places to look for life outside our solar system.
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