A Saturnian satellite joins the club of moons with oceans. A subsurface sea might hide beneath the icy crust of Dione, a moon of Saturn, researchers report online September 28 in Geophysical Research Letters. That puts Dione in good company alongside Enceladus (another moon of Saturn), several moons of Jupiter and possibly even Pluto.
Dione’s ocean is about 100 kilometers below the surface and is roughly 65 kilometers deep, Mikael Beuthe, a planetary scientist at the Royal Observatory of Belgium in Brussels, and colleagues report. They inferred the ocean’s presence from measurements of Dione’s gravity made by the Cassini spacecraft, which has been in orbit around Saturn since 2004.