Saturnís retrograde moon Phoebe

Saturnís retrograde moon Phoebe

Fig. 10.28 . This image of Phoebe suggests that the moon may be an ice-rich body coated with a thin layer of dark material, resembling the nucleus of comets. Small bright craters in the image are probably young features. When impacting projectiles slammed into the surface of the moon, the collisions excavated fresh, bright material, probably water ice, underlying the surface area. Dark material on some crater walls appears to have slid downwards, exposing more light-colored material. Phoebe orbits Saturn in the backward retrograde direction to all of the other mid-sized satellites of the planet, and the moonís dark and irregular, cratered surface, retrograde orbit, and low mean mass density suggest that Phoebe was once part of the Kuiper belt of icy comets beyond Neptune before passing near Saturn and being captured by its gravity. This mosaic of two images was acquired from the Cassini spacecraft during its Phoebe flyby on 11 June 2004. (Courtesy of NASA/JPL/SSI.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University