Enceladus: Structures & Vocabulary

Enceladus is a small icy moon of Saturn with active jets erupting from fractures near its south pole. Measurements indicate a global salty subsurface ocean beneath the ice shell, making Enceladus one of the most accessible ocean worlds because material from the ocean is naturally expelled into space.

Orbital resonance and eccentricity allow Saturn's gravity to flex Enceladus as it orbits, dissipating mechanical energy as heat. Tidal heating helps keep water liquid and may drive circulation through a porous rocky core. Pressure and fracture pathways allow ocean-derived material to reach the surface and erupt.

Cassini imaged active plumes, measured enhanced thermal emission from south-polar fractures, and flew through the plume repeatedly. Its instruments detected water, salts, silica particles, molecular hydrogen, and organic compounds consistent with a warm water-rock interaction system beneath the surface.

The surface includes ancient cratered terrain and younger tectonically deformed regions. Near the south pole, parallel “tiger stripe” fractures are unusually warm and feed jets of vapor and ice grains. Gravity and libration measurements indicate a global subsurface ocean beneath the ice shell.