The K2-18b “Biosignature” Anomaly: The Exoplanet That’s Breaking the Internet
Few astronomical discoveries have generated as much excitement—and confusion—as K2-18 b . Located roughly 120–124 light-years away in the constellation Leo, this unusual exoplanet has become one of the most closely watched worlds beyond our Solar System. It is larger and more massive than Earth, yet smaller than Neptune, and it orbits within the habitable zone of its cool red dwarf star. Then came the James Webb Space Telescope. JWST detected methane and carbon dioxide in K2-18 b's atmosphere. Later observations with the telescope's MIRI instrument produced a tantalizing spectral feature that could be explained by dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) —molecules considered potential biosignatures. In 2025, one research team reported evidence at roughly the 3-sigma level. Suddenly, headlines started appearing that seemed to suggest something extraordinary: Could JWST have found evidence of life on another planet? Not quite. And this is where the story ...