... Saturns Iapetus: Moon with a Strange Surface . ... Credit: Cassini Imaging Team , SSI , JPL , ESA , NASA Explanation: What has happened to Saturn's moon Iapetus? A strange ridge crosses the moon near the equator, visible near the bottom of the above image, making Iapetus appear similar to the pit of a peach . Half of Iapetus is so dark that it can nearly disappear when viewed from Earth. ... The other half of Iapetus is relatively bright but oddly covered with long and thin streaks of dark. ...