spacetoday.net: Enceladus plumes linked to tidal friction

Posted: Thu, May 17, 2007, 5:39 AM ET (0939 GMT)
Enceladus seen by Cassini in July 2005 (NASA/JPL)

Frictional heating along fault lines on the surface of Saturn's moon Enceladus may be the explanation for plumes of vapor emitted by the moon, scientists said this week. In a paper published in the current issue of the journal Nature, scientists said that tidal forces created by the moon's eccentric orbit around Saturn cause fault lines in the icy moon's outer shell to flex, generating heat through friction. That heat causes ice to sublimate, and in turn escapes in the form of plumes that have been detected by NASA's Cassini spacecraft. The mechanism doesn't require the presence of liquid water to generate the plumes, but does suggest that a liquid water ocean exists below the moon's icy shell, allowing the shell to move enough to generate the required frictional heating.