Dione (moon)
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Dione is the fourth-largest moon of Saturn. With a mean diameter of 1,123 km and a density of about 1.48 g/cm3, Dione is composed of an icy mantle and crust overlying a silicate rocky core, with rock
Dione photographed by the Cassini spacecraft in 2008
Giovanni Domenico Cassini, discoverer of Dione
Size comparison of Earth, the Moon, and Dione.
Dione in true color.
Callisto (moon)
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Callisto is the second-largest moon of Jupiter, after Ganymede. It is also the third-largest moon in the Solar System, following Ganymede and Saturn's moon Titan, and nearly as large as the planet Mer
Size comparison of Earth, Moon and Callisto
Galileo image of cratered plains, illustrating the pervasive local smoothing of Callisto's surface
Impact crater Hár with a central dome. Chains of secondary craters from formation of the more recent crater Tindr at upper right crosscut the terrain
Voyager 1 image of Valhalla, a multi-ring impact structure 3,800 km in diameter