James Webb Detects a 99.7% Possible Life Signal From a Nearby Planet

#JamesWebb #K218b #AlienLife A planet about 120 light-years away produced one of the most exciting signals in the search for life beyond Earth. In 2025, one analysis of James Webb data reported a roughly three-sigma hint of dimethyl sulfide or dimethyl disulfide in the atmosphere of K2-18 b — molecules that drew attention because DMS on Earth is strongly associated with life. But 99.7 percent did not mean scientists were 99.7 percent certain they had found life. Tonight we follow that signal from the atmosphere of a distant sub-Neptune into the statistics behind the headline. We will see how Webb reads molecules from starlight, why a three-sigma result is still considered tentative, and why later independent analyses found the proposed biosignature far less convincing. K2-18 b remains fascinating. But the evidence for life is not confirmed, and the real story is how science separates an extraordinary possibility from a discovery. Sources: a. Madhusudhan et al. — New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI — The Astrophysical Journal Letters, 2025 — DOI: 10.3847/2041-8213/adc1c8 b. Luque et al. — Insufficient Evidence for DMS and DMDS in the Atmosphere of K2-18 b — Astronomy & Astrophysics, 2025 — DOI: 10.1051/0004-6361/202555580 c. Stevenson et al. — K2-18b Does Not Meet the Standards of Evidence for Life — The Astronomical Journal, 2025 d. Welbanks et al. — Challenges in the Detection of Gases in Exoplanet Atmospheres — Nature Astronomy, 2025 e. NASA/ESA/CSA Webb — Methane and Carbon Dioxide in the Atmosphere of K2-18 b f. Schmidt et al. — A Comprehensive Reanalysis of K2-18 b’s JWST NIRISS+NIRSpec Transmission Spectrum — The Astronomical Journal #Space #Astronomy #Science #Exoplanets #Astrobiology #JWST #Biosignatures #Universe