Enceladus: Observation, Measurement & Evidence

The moon has an icy crust, a global ocean beneath it, and a rocky core. The south-polar terrain contains warm fractures called tiger stripes where plumes vent water vapor, ice grains, salts, and organic compounds. Ejected ice also contributes material to Saturn's E ring.

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.

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 flew through the plume and detected water, salts, silica particles, organic compounds, molecular hydrogen, and other species. Heat maps, gravity, imaging, and libration measurements independently support ongoing activity and an ocean rather than a short-lived surface frost phenomenon.