Phoebe. Mosaic of two images of Saturn's largest outer moon Phoebe, imaged by NASA's Cassini spacecraft, showing the region (120km diameter) near the south pole. Many craters, which are caused by the impact of meteorites, can be seen on the surface, some with walls as high as 4km. The bright white areas are thought to be ice, which is evidence for the theory that Phoebe is an ice- rich body, covered with a layer of dark material. The Cassini-Huygens spacecraft was launched in 1997 to investigate Saturn, its rings and its moons. This image was taken during Cassini's flyby on 11th June 2004 at a distance of 13,000km.