Skepticism greets claims of a possible biosignature on a distant world

Researchers recently found the strongest evidence yet of a "biosignature" on exoplanet K2-18b, suggesting potential life due to detected methane and carbon dioxide in its hydrogen-rich atmosphere. However, skeptics point out alternative chemistry explanations for these gases without biological activity, and the planet's properties are consistent with various types, not just a hycean planet with an ocean that could sustain life. Confirming a biosignature is challenging due to multiple factors including the planet's orbital location within its star's habitable range.