That 'alien' signal we found on a distant water-world might just be a boring cloud of gas we misidentified.
March 23, 2026
Original Paper
Three outstanding physical questions for K2-18 b and other temperate sub-Neptunes
arXiv · 2603.19803
The Takeaway
When the James Webb Space Telescope detected signs of dimethyl sulfide on exoplanet K2-18 b, it caused a global stir because that gas is only produced by life on Earth. New research suggests that what we actually saw was a common chemical 'mimic,' reminding us how easily nature can trick us into seeing signs of life where none exist.
From the abstract
Recent transmission spectra of the temperate sub-Neptune K2-18 b obtained with JWST have attracted significant attention. Debates have quickly arisen over the interpretation of the spectral data, particularly the recent MIRI observation where dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) are claimed. Here we revisit K2-18 b as a case study to examine several key questions that are also broadly relevant to the temperate sub-Neptune population: i) Can the low water abundance be reconciled w