Dione (moon) - Physical Characteristics

Physical Characteristics

At 1122 km in diameter, Dione is the 15th largest moon in the Solar System, and is more massive than all known moons smaller than itself combined. It is composed primarily of water ice, but as the third densest of Saturn's moons (after Enceladus and Titan, whose density is increased by gravitational compression) it must have a considerable fraction (~ 46%) of denser material like silicate rock in its interior.

Though somewhat smaller and denser, Dione is otherwise very similar to Rhea. They both have similar albedo features and varied terrain, and both have dissimilar leading and trailing hemispheres. Dione's leading hemisphere is heavily cratered and is uniformly bright. Its trailing hemisphere, meanwhile, contains an unusual and distinctive surface feature: a network of bright ice cliffs.

Scientists recognise Dionean geological features of the following types:

• Chasmata (chasms; long, deep, steep-sided depressions)
• Dorsa (ridges)
• Fossae (long narrow depressions)
• Craters
• Catenae (crater chains)