Martian regolith may block Earth microbes, tardigrades reveal through soil tests

Researchers exposed tardigrades to two Martian regolith simulants (MGS-1 and OUCM-1). MGS-1 caused notable stress and rapid dormancy, while OUCM-1 was less harmful. Washing the simulant reduced toxicity, indicating a water-soluble component—likely salts—drives the harm. The results suggest Mars’ soil chemistry could help prevent Earth microbes from contaminating the planet (a planetary-protection bonus), while also implying that treating regolith could eventually support plant growth on Mars.