In a significant development in the search for life beyond Earth, scientists using NASA’s James Webb Space Telescope (JWST) have detected the presence of dimethyl sulfide (DMS) or dimethyl disulfide (DMDS) in the atmosphere of a distant exoplanet named K2-18b. Both molecules are known to be associated with biological activity on Earth, where they are primarily produced by marine phytoplankton and bacteria. Although not definitive proof of life, the discovery marks a critical milestone in the hunt for biosignatures in outer space.
Located 124 light years away in the Leo constellation, K2-18b is a sub-Neptune-sized exoplanet orbiting a red dwarf star. The planet lies within the habitable zone, raising hopes about its potential to support life. Professor Nikku Madhusudhan from the University of Cambridge, who led the research, said he is cautiously optimistic. “We hope to obtain more substantial evidence soon,” he told the BBC, emphasising the need for further analysis to confirm whether the detected molecules truly originate from biological processes.
JWST: A Window into Alien Worlds
The recent detection adds to JWST’s growing reputation as a game-changer in exoplanet research. In September 2023, the telescope identified methane and carbon dioxide in K2-18b’s atmosphere, carbon-bearing molecules that suggest the possibility of life-supporting environments. These findings also hinted at a potential ocean-covered surface, strengthening the theory that K2-18b may be part of a new category of potentially habitable planets called Hycean worlds.
Earlier, the Hubble Space Telescope had picked up signs of a hydrogen-rich atmosphere, though its composition remained unclear. JWST’s advanced infrared capabilities have helped refine those findings and detect more complex compounds like DMS. While the new data is compelling, scientists caution against jumping to conclusions without ruling out non-biological sources for the chemicals observed.
Other Groundbreaking Clues of Life Beyond Earth
K2-18b isn’t the only candidate showing potential signs of habitability. Over the years, multiple missions have uncovered tantalising hints on other celestial bodies. NASA’s Cassini mission to Saturn's moon Enceladus, for instance, revealed water-rich plumes containing organic molecules, carbon dioxide, methane, and phosphates, key ingredients for life. The discovery of hydrothermal activity on Enceladus’ ocean floor has further boosted interest in the moon’s potential to harbor microbial life.
Closer to home, NASA’s Curiosity rover found geological evidence suggesting ancient, shallow lakes once existed on Mars. Symmetrical ripple patterns and the recent discovery of siderite in the Gale Crater point to a time when Mars possibly had a carbon dioxide-rich atmosphere capable of supporting life.
