Saturns Moon Rhea from Cassini . ... Credit Copyright: Cassini Imaging Team , SSI , JPL , ESA , NASA Explanation: Each moon of Saturn seems to come with its own mystery . Rhea, Saturn's second largest moon behind Titan , shows unusual wisps, visible above as light colored streaks. ... Rhea's rotation and orbit are locked together, just like Earth's Moon , so that one side always faces Saturn . A consequence of this is that one side always leads the other. ... NASA Official: Jay Norris. ...