Hycean Worlds: New Biosignature Could Speed Up the Search for Extraterrestrial Life

Astrobiologists propose that methyl halides, a group of chemicals produced by some bacteria and marine algae on Earth, could be a biosignature in the atmosphere of Hycean worlds. These hypothetical planets, characterized by hydrogen-rich atmospheres and deep liquid water oceans, offer a potentially clearer signal for detecting life than Earth-like planets. A team from the University of California, Riverside, and ETH Zurich suggests that conditions on Hycean planets may allow methyl halides to accumulate in large quantities in the atmosphere. Methyl halides have strong absorption characteristics in infrared light, making them detectable by the James Webb Space Telescope (JWST) in as little as 13 hours. The best candidate for a Hycean world is K2-18b, an exoplanet 124 light-years from Earth. While the existence and habitability of Hycean worlds remain uncertain, the detection of methyl halides could indicate life in their oceans. If life exists on such worlds, organisms would likely be anaerobic, breathing hydrogen instead of oxygen. Hycean worlds may be more common than Earth-like planets, potentially expanding the search for life in the galaxy.