The Webb Space Telescope released findings that the atmosphere of K2-18 b, an exoplanet 8.6 more massive than earth, contains carbon-bearing molecules including methane and carbon dioxide. This suggests that the planet could be a Hycean exoplanet, a planet with a hydrogen-rich atmosphere and water ocean-covered surface.
K2-18 b orbits the cool dwarf star K2-18 in the habitable zone and lies 120 light-years from Earth in the constellation Leo. Exoplanets such as K2-18 b, which have sizes between those of Earth and Neptune, are unlike anything in our solar system. This lack of equivalent nearby planets means that these 'sub-Neptunes' are poorly understood, and the nature of their atmospheres is a matter of active debate among astronomers.
The suggestion that the sub-Neptune K2-18 b could be a Hycean exoplanet is intriguing, as some astronomers believe that these worlds are promising environments to search for evidence for life on exoplanets.
Even more tantalizing is an initial, "less robust" inference from the data that the atmosphere may contain a molecule called dimethyl sulfide (DMS). On Earth, this molecule is only produced by life. Most of the DMS present in Earth atmosphere is produced by ocean-dwelling phytoplankton.
While there is excitement about this possibility, it is too early to make a determination about the presence of DMS. However, more data is on the way.
"These results are the product of just two observations of K2-18 b, with many more on the way," explained team member Savvas Constantinou of the University of Cambridge. "This means our work here is but an early demonstration of what Webb can observe in habitable-zone exoplanets."
Ryan McDonald, a NASA Sagan Fellow at the University of Michigan took to BlueSky to thoroughly explain reasons to be skeptical about these possible signs of life on K2-18 b at this point, here.
A video from Cambridge University:
