In a cosmic hit and run, Saturn's moon may have flipped

Mar 2012
New Hampshire
Enceladus – a large icy, oceanic moon of Saturn – may have flipped, the possible victim of an out-of-this-world wallop.

While combing through data collected by NASA's Cassini mission during flybys of Enceladus, astronomers from Cornell, the University of Texas and NASA have found the first evidence that the moon’s axis has reoriented, according to new research published in Icarus. Examining the moon’s geological features, the group showed how Enceladus appears to have tipped away from its original axis by about 55 degrees.

An asteroid may have struck the moon’s current south polar region when it was closer to the equator in the past. “The geological activity in this terrain is unlikely to have been initiated by internal processes,” he said. “We think that, in order to drive such a large reorientation of the moon, it's possible that an impact was behind the formation of this anomalous terrain.” Wobbly, rickety and unsteady after an asteroid’s smack, the physics of Enceladus’ rotation would have eventually re-established stability, a process that likely took over a million years. To do that, the north-south axis needed to change – a mechanism called “true polar wander.”