Beneath the most cratered and seemingly lifeless face in the Saturn system, scientists have found a global ocean younger than the Himalayas—detected not by sight, but by the subtle mathematics of a moon's wobble. Using archival data from NASA's Cassini spacecraft, researchers reconstructed Mimas's orbital motion with enough precision to rule out every explanation but one: a liquid interior decoupled from its frozen shell. The discovery asks us to reconsider what an ocean world is allowed to look like, and reminds us that the solar system conceals its most consequential secrets beneath the most