Two-faced Iapetus

Two-faced Iapetus

. Saturnís outermost large moon, Iapetus, has a bright, heavily cratered terrain and a dark landscape, as shown in this Voyager 2 image taken on 22 August 1981. The bright regions are probably made of water ice, and the dark substance may be composed of organic substances. Iapetus apparently plows through the dark material as it orbits Saturn, covering the lead, frontal hemisphere of the satellite. (Courtesy of NASA and JPL.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University