A team of astronomers using the James Webb Space Telescope has detected what could be the most compelling evidence yet of a potential biosignature—an indicator of life—on a distant exoplanet named K2-18b.
Located 124 light-years from Earth, K2-18b is believed to be a Hycean world—a type of planet hypothesized to be covered in vast oceans with a hydrogen-rich atmosphere. Crucially, it resides within the habitable zone of its star, where conditions could allow liquid water to exist on the surface.
The research team, led by Professor Nikku Madhusudhan of the University of Cambridge, identified the presence of dimethyl sulfide (DMS) and possibly dimethyl disulfide (DMDS) in the planet’s atmosphere. On Earth, these molecules are only known to be produced by marine microbial life. Their detection marks a significant moment in the search for extraterrestrial life.
“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,” said Madhusudhan.
However, the scientists are proceeding with caution. They acknowledge that the molecules could also result from unknown chemical processes unrelated to life.
The findings, published in The Astrophysical Journal Letters, build on previous detections of carbon dioxide and methane on K2-18b. The latest observations were made using Webb’s Mid-Infrared Instrument, adding a fresh layer of evidence from an independent data set.
The possibility of life beyond Earth remains unconfirmed—but the search just got a lot more exciting.
