NASA found fungal strains that survive even its most stringent sterilization efforts, suggesting Earth microbes may already be living on Mars.
When exploring worlds which could plausibly harbor life — Enceladus, Europa, Mars, Titan — space agencies employ protocols to prevent Earth-based microbes contaminating any biology elsewhere.
The existence of near-unkillable fungi makes future Mars rover missions more fraught and past ones potential seeds of terrestrial life on the red planet. Titan may likewise be compromised: When visited by the Cassini-Huygens orbiter in 2004, no one realized Saturn’s moon had liquid oceans and was thus a promising candidate for life, so the probe was not fully sterilized. The little spacecraft “might be seeding life,” a mission scientist told Flagship’s Tom in 2017.