for National Geographic News
Scientists may have found the source of towering geysers on Saturn's moon Enceladusbut the discovery could be a setback for hopes of life on the distant satellite.
Enceladus's plumes of icy water vapor have intrigued observers since they were spotted by NASA's Cassini spacecraft in 2006.
Some have theorized that the geysers are caused by underground liquid water that freezes instantly when it is jettisoned into space.
If reservoirs of subsurface water exist on Enceladus, so might primitive life forms.
But two papers published in the May 17 issue of the journal Nature suggest that the geysers are caused by the friction between massive plates of ice.
The new studies suggest that ice plates tens of kilometers deep periodically grind together at fault lines on the moon's surface.
The heat created by this friction may turn the ice directly into vapor, thereby producing the geysers.
"The two sides are rubbing backwards and forwards against each other," said Francis Nimmo, a planetary scientist at the University of California, Santa Cruz, and lead author of one study.
"Just like when you rub your hands together, you get heat—that is how we think the ice is being heated up."
Saturn's Internal Ocean
The plates of ice may be moving because of the tug from Saturn's gravitational pull. (See pictures of Saturn from Cassini.)
"Enceladus's orbit isn't quite circular," Nimmo said. "As it goes around Saturn the distance between them is changing, so Saturn's gravitational attraction is changing."
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