Free Astronomy Magazine July-August 2025

4 JULY-AUGUST 2025 ASTRO PUBLISHING through the media, as dimethyl sul- fide is a gas also present on Earth, where it is synthesized almost ex- clusively by microorganisms. That was enough to make people shout about the discovery of life on an- other planet. O n April 16, a team of as- tronomers from the Uni- versity of Cambridge (UK) announced the discovery of di- methyl sulfide in the atmosphere of the exoplanet K2-18 b. That announcement quickly went viral by Michele Ferrara revised by Damian G. Allis NASA Solar System Ambassador Life unlikely on K2-18 b But what is the current state of things? Now a few months past the imprudent enthusiasm that has per- vaded the generalist information (or disinformation) media, and after supporters and skeptics alike have had time to express their opin- ions on the subject, we will try to put some order on the issue so that each reader can have their own in- formed opinion on what the Cam- bridge astronomers claimed to have discovered. I n the background, the possible appearance of a hycean world, a new class of planets similar to sub-Neptunes, but with a surface entirely covered by an ocean, topped by a thick atmosphere rich in hydrogen. So far, no hycean planet has been definitively confirmed. Only about fifteen candidates are known, in- cluding K2-18 b. [Amanda Smith, University of Cambridge]