A new investigation with NASA’s James Webb Space Telescope into K2-18 b, an exoplanet 8.6 times as massive as Earth, has revealed the presence of carbon-bearing molecules including methane and carbon dioxide. Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet, one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface.
Uranus and Neptune both have a significant amount of methane, as does Titan.
It’s probably the mix of all the gasses (including the dimethyl sulfide tentative finding) that makes it exciting. Methane isn’t a bio-signature on its own.