Dione

Slightly smaller than Rhea, Dione is the largest of the inner moons.

Because their composition and surface features are similar, Dione and Rhea are sometimes referred to as sisters, with Rhea called 姐 姐 "Jie Jie" (big sister), and Dione called 妹 妹 "Mei Mei" (little sister).

Composition
Even though it is the third densest moon, early surveys confirmed that Dione was strongly differentiated, with most of the silicate rock and other heavy elements deep inside under miles of water ice. Unlike Enceladus, no deep fissures offered access to these precious heavy elements, and consequently Dione has never had a permanent human presence.

Surface Features

 * Chasmata (chasms; long, deep, steep-sided depressions) These features are most common on the trailing hemisphere.
 * Dorsa (ridges)
 * Fossae (long narrow depressions)
 * Craters
 * Catenae (crater chains)