Phoebe. Mosaic of six images of Saturn's largest outer moon Phoebe, taken by NASA's Cassini spacecraft. It is believed that Phoebe may originally have belonged to a population of icy comet-like bodies, some of which now reside in the Kuiper belt beyond Neptune. It has an average diameter of 214 kilometres but its cratered surface gives it an irregular topography. The variation of brightness on the surface indicates that there may be ice present. The Cassini-Huygens spacecraft was launched in 1997 to investigate Saturn, its rings and its moons. These images were taken during Cassini's flyby on 11th June 2004. The craft passed at a distance of 2,000km.