Photograph Description

Dione, also known as Saturn IV, was discovered by Giovani Cassini in 1684. It has a diameter of 1,118 kilometres and is the densest of Saturn’s moons, so although it is composed mainly of water ice, it must have a large amount of denser material such as silicate rock in its interior. This image was taken as part of the Cassini-Huygens mission, which launched in 1997 with the purpose of studying Saturn and its moons. Image taken on 27 October 2004 at a distance of 1.2 million kilometres by a narrow angle camera aboard the Cassini orbiter. (Photo by Science Photo Library)