page_title: Dione (moon)
section_title: Physical characteristics and interior
hierarchical_section_title: Dione (moon) / Physical characteristics and interior
caption_attribution_description: English: Diameter comparison of Saturn's moon Dione, the Moon and Earth Scale approx. 29km per px.
context_page_description: Dione is a moon of Saturn. It was discovered by Italian astronomer Giovanni Domenico Cassini in 1684. It is named after the Titaness Dione of Greek mythology. It is also designated Saturn IV.
context_section_description: At 1122 km (697 mi) in diameter, Dione is the 15th largest moon in the Solar System, and is more massive than all known moons smaller than itself combined. About two thirds of Dione's mass is water ice, and the remaining is a dense core, probably silicate rock.
  Data gathered by Cassini indicates that Dione has an internal liquid salt water ocean (a situation similar to that of its orbital resonance partner, Enceladus). Downward bending of the surface associated with the 1.5 km high ridge Janiculum Dorsa can most easily be explained by the presence of such an ocean. Gravity and shape data points to a 99 ± 23 km thick ice shell crust on top of a 65 ± 30 km thick internal liquid water global ocean. Neither moon has a shape close to hydrostatic equilibrium; the deviations are maintained by isostasy. Dione's ice shell is thought to vary in thickness by less than 5%, with the thinnest areas at the poles, where tidal heating of the crust is greatest.
  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, however, 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 or canyons)
  Dorsa (ridges)
  Fossae (long narrow depressions)
  Craters
  Catenae (crater chains)
caption: Size comparison of Earth, the Moon, and Dione.
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