Enceladus (Saturn II) A major satellite of Saturn, discovered in 1789 by Sir William Herschel. It has the brightest surface of any body in the solar system (albedo more than 0.9), composed of clean, fresh ice (not necessarily water ice). The surface is cratered, but there are also smooth plains and long linear cracks and ridges. The surface appears to be young, probably less than 100 Ma old, indicating it has been geologically active until very recently, and possibly is still active with some kind of water volcanism. This activity may make Enceladus the source of the material comprising the tenuous E ring of Saturn. Enceladus is much too small to be heated by radioactive decay; the heat would have dissipated long ago. The orbit of Enceladus is locked in a 1:2 resonance with Dione, which may provide some tidal heating, but probably not enough to melt water ice. Enceladus is 238 020 km from Saturn; its radius is 249.1 km; mass 0.73 × 10 ²⁰ kg; mean density 1120kg/m³; visual albedo 1.0.

Enceladus in Greek mythology, a giant killed by Athene. His name was used for a satellite of Saturn, the eighth closest to the planet and probably composed mainly of ice, discovered by W. Herschel in 1789.