Enceladus' surface. Coloured Cassini spacecraft image of the surface of Enceladus, one of Saturn's moons. The large impact crater at top measures 21 kilometres in diameter. Blue areas are thought to be outcrops of solid ice or ice with a different grain size to that on the surface that has been exposed by fractures in the surface. Enceladus is composed of water ice, silicates and iron. Its surface features suggest the presence of a subsurface ocean, although this has not been confirmed. The Cassini-Huygens spacecraft was launched in 1997 to investigate Saturn, its rings and its moons. This image was taken at a distance of 21,300 kilometres on 9 March 2005.