Dr. Daniel Storey

Is There a Sign of Life on K2-18 b? Maybe—But It's Far from Certain A new study by Madhusudhan et al., published in Astrophysical Journal Letters, reports a possible detection of gases—dimethyl sulfide (DMS) or dimethyl disulfide (DMDS)—in the atmosphere of the exoplanet K2-18 b. On Earth, these gases are often linked to biological activity, making the claim intriguing. However, the signal is weak and open to other explanations, including instrument noise or natural (non-biological) processes. In fact, scientists have even detected DMS on a lifeless comet, showing that biology isn't the only possible source. There’s also a bigger challenge: we still know very little about the planet itself. That makes it difficult to say what any particular atmospheric signal really means. Still, this research matters—not because it proves life exists on K2-18 b, but because it shows scientists where to look more carefully, what tools need improvement, and what kinds of evidence we’ll need to be more confident in the future. This is not a discovery of alien life. It’s not even a strong hint. But it is a step forward in figuring out how we might one day make that discovery—and how to do it right. Illustration credit: NASA, ESA, CSA, Joseph Olmsted (STScI) seti.org/biosignatures-k2-18…