Examination has also shown the surface to be relatively smooth; the few objects that seem to be impact craters appeared to have been filled in, perhaps by raining hydrocarbons or volcanoes.
Examinarea a arătat, de asemenea, că suprafața este relativ netedă, cu puține obiecte care par să fie cratere de impact care au fost umplute, probabil de ploi de hidrocarburi sau de către vulcani.