Mimas Rewrites Its Story: A Young Global Ocean Beneath Icy Craters

A reanalysis of Cassini data reveals Saturn’s moon Mimas hosts a global ocean beneath 20–30 km of ice, likely formed in under 25 million years, inferred from precise libration and periapsis drift rather than direct water detection. The young ocean explains Mimas’s motion better than solid-body models, even though the surface remains heavily cratered and deceptively inactive. This makes Mimas a potential early-stage ocean world, offering new insights into how oceans can emerge under thick shells, while many details (chemistry, depth, persistence) remain uncertain and could be refined by future missions.