Dione is a natural satellite of Saturn discovered in 1684 by Giovanni Cassini. Its name comes from Greek mythology. Dione is mainly made up of frozen water. However, since Dione is Saturn's densest moon (apart from Titan, whose density is higher by gravitational compression), it must surely have denser materials inside, such as silicon rocks. Although a little smaller, Dione is a moon very similar to Rhea. Both have similar compositions and albedo characteristics, and both exhibit asymmetries in their front and back hemispheres. Dione's front hemisphere is highly craterized and uniformly shiny. Its rear hemisphere contains a network of bright lines, although not very well defined, on a sea with a dark background.
