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Saturns Moon Spews Fountains of Water Ice

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Saturn Moon Spews Fountains

By Irene Mona Klotz, Discovery News



Dec. 1, 2005— A mysterious energy source is heating up the southern pole of Saturn's moon Enceladus, triggering blasts of highly pressurized water ice that is spewing hundreds of miles into space, say scientists who this week released pictures of the fountains taken by the Cassini satellite.


"This is one of the most extraordinary discoveries for us," said Carolyn Porco, a planetary scientist at the Space Science Institute in Boulder, Colo., who heads the Cassini imaging team.


Cassini captured images of the geysers with a back-lit view of Enceladus as the spacecraft made a pass by the moon last weekend.


Scientists earlier had discovered the moon's southern hot spot, relatively speaking. Temperatures around Enceladus' south pole are about -163° Celsius (-261° Fahrenheit), compared to -198° Celsius (-325° Fahrenheit) for the rest of the moon.



The team suspected there could be some geologic activity and set up the camera angle to take advantage of the sun-moon geometry. They were richly rewarded with a series of shots showing fountains blasting from the moon's surface to a height of about 500 kilometers (311 miles), Porco said.


"We suspect it could be caused by cold vents that lead from somewhere in the subsurface, perhaps as far as 1 kilometer (.62 mile) down. Water ice is sublimating (changing directly from a solid to a gas state) and the vapors are coming off and building up to high pressure," Porco said.


The vapors rise to the surface as a jet and blast. The images taken by Cassini show particles of powder-sized ice scattering, much as a stream of dust is illuminated by sunlight flowing through a window.


The jets are formed like comet tails, except that Enceladus has some sort of internal heating mechanism to transform its ice into vapor, rather than the solar energy that heats up a comet.


Another possibility is that Enceladus' energy source is even hotter than suspected and the water ice is actually melted into an underground liquid that is creating hot springs, similar to the geysers found at Yellowstone National Park and elsewhere on Earth.


"What's puzzling us is how it's getting hot enough," Porco said. "We're still in a quandary over how you'd get this much energy."


The findings buttress theories that Enceladus is providing the material for Saturn's E-ring, which was first observed in images taken by Cassini in January.


The scientists are continuing their analysis of the fountains and looking for additional opportunities to gather more information during future Cassini flybys.

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