NASA’s James Webb Space Telescope has uncovered the presence of methane and carbon dioxide on K2-18 b, an exoplanet approximately 8.6 times the size of Earth. This finding hints at the possibility that K2-18 b might be a Hycean exoplanet, characterized by a hydrogen-rich atmosphere and a surface covered by water oceans. The initial insights into this habitable-zone exoplanet’s atmosphere were first obtained using NASA’s Hubble Space Telescope, leading to further investigations that have reshaped our understanding of the system.

Located 120 light-years away in the Leo constellation and orbiting the cool dwarf star K2-18, K2-18 b falls into the category of “sub-Neptunes,” which are quite distinct from any planets in our solar system. These sub-Neptunes remain a puzzle for astronomers due to their unique characteristics and atmospheres, sparking ongoing debates among scientists. The recent discovery of methane, carbon dioxide, and the absence of ammonia on K2-18 b supports the idea that it might harbor a water ocean beneath its hydrogen-rich atmosphere. Intriguingly, observations also suggest the potential presence of a molecule called dimethyl sulfide (DMS), a substance typically associated with life on Earth, further fueling excitement about the possibility of finding life beyond our planet. NASA’s James Webb Space Telescope continues to unravel the mysteries of the cosmos, shedding light on distant worlds and their potential for hosting life.