Dione (moon)

Dione is one of the moons of Saturn, discovered by the Italian astronomer Giovanni Domenico Cassini in 1684. It is the fifteenth-largest moon in the solar system and is primarily composed of water ice with a smaller amount of rocky material. Dione has a diameter of about 1,123 kilometers (698 miles). Dione's surface features a mix of heavily cratered areas and relatively smooth regions, suggesting a history of geological activity.