December 17, 2004
One hemisphere of Iapetus is covered with very reflective material while
the other hemisphere is covered with some of the darkest material in the
solar system. The leading hemisphere of Iapetus (the side that faces the
direction of rotation) is very dark, reflecting only about 4 percent of
the sunlight that falls on it. The trailing hemisphere reflects about 50
percent of the sunlight that falls on it.