Two-Toned Moon

Iapetus is one of the oddest moons in the solar system. One hemisphere of the large moon of Saturn is almost pure white, coated by ice. The other, glimpsed at right in this image from the Cassini spacecraft, is almost as dark as coal. In addition, a tall ridge encircles the moon's equator (visible at far right), while a large impact basin scars its southern hemisphere (lower left). Recent simulations hint at a violent past for the moon. [NASA/JPL/SSI]