The first stuff I saw about Webb's K2-18b observations were about methane in its atmosphere, and that seemed quite meh - methane is common. Here it says it also may have seen traces of life-related compounds.
So quite a bit more of a big deal. It's not a certain finding, though.
Atmospheric oxygen in large quantities would be a definitive proof of life - though Earth didn't have that for the first 2 billion years until photosynthesis started.
@osma
Not a certain finding is an understatement, the same group that hype this very marginal detection had shown that the systematic uncertainty in JWST line strength can be an order of magnitude! Even if, by pure chance, this result turns out to be correct the credit for discovery should not be awarded to their paper.
