The Surfaces of Small Saturnian Satellites: What Causes the Range of Morphologies?

The Cassini spacecraft has observed irregularly shaped Saturnian satellites Phoebe, Hyperion, Telesto, Helene, and several ring-related satellites in sufficient detail to show a surprising range of surface morphologies for objects too small to have internally driven processes. Hyperion's sponge-like appearance derives from a high density of well preserved craters 3-12 km in diameter. Telesto has essentially buried itself in debris, and Phoebe appears generally similar to some of the larger satellites except for its overall irregular shape. Effects on the morphology of craters, ejecta dispersal, and seismic attenuation from the combination of surface gravity and likely porosities appear to provide the best explanation for the differing surface characters of these objects.