Magazine article Science News

Gassy Geysers: Cassini Surveys Saturn's Moon

Magazine article Science News

Gassy Geysers: Cassini Surveys Saturn's Moon

Article excerpt

Data from NASA'S Cassini spacecraft raise new questions about the origin of Saturn's tiny moon Enceladus and the heat driving its plume of ice and water vapor.

Cassini lived to tell the tale of its March 12 brush with the enormous plume of ice, water vapor, and gas spewing from several fissures near the south pole of the moon. Swooping as close as 50 kilometers, Cassini went in like a dog with its tongue flapping out the window, sniffing and tasting the gassy brew for clues to the plume's origins and composition.

Astronomers had been astonished in 2005 to learn of the giant plumes of ice and water vapor blasting from the "tiger stripe" cracks in Enceladus' southern hemisphere, and the detection of organic compounds in the gassy mix suggested the moon could support life.

The March 12 fly-through, described at a NASA media briefing this week, got a closer look at the plumes and the moon's surface. Heat maps generated from the new data suggest that at least three of the tiger-stripe fissures are warm along their entire lengths and are ejecting water molecules at speeds faster than 600 meters per second.

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The brightest fracture, dubbed Damascus Sulcus, registered temperatures as high as 180 kelvins. That's more than 100 kelvins hotter than elsewhere in the polar region. Calculations published in Nature last year suggested that the little moon's heat comes from friction generated when the fissures' walls rub against each other as Saturn exerts its gravitational pull. …

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