Cassini Spacecraft to Fly Through Moon's Geyser

Cassini Spacecraft to Fly Through Moon's Geyser
An unprocessed image of Enceladus taken on April 24, 2007.
(Image: © NASA/JPL/Space Science Institute)

The Cassinispacecraft will perform its closest flyby ever of Saturn's ice-spewing moonEnceladus early next year, moving directly into its icy polar geyser for a deep-spaceshower.

Cassini's third flyby of Enceladus (en-SELL-ah-dus), set forMarch 2008, will swing it within 19 miles (30 kilometers) of the saturnian moon?almostsix times closer than the spacecraft's closest pass to it in 2005. The tighttrajectory will move Cassini directly into the icygeyser at the moon's southern pole, said NASA official James Green during ateleconference today.

"Cassini was never designed to flythis close, but we've just got to get in that plume and look at that materialand see what it is and where it's coming from," said Green, director of NASA's Planetary Division in Washington,D.C.

Scientists thinkthe geyser is 90 percent fine water-icecrystals, but suspect ammonia and methane gas are present as well.

Althoughthe flyby isn't without risk, Alan Stern, associate administrator for NASA'sScience Mission Directorate in Washington, D.C., said Cassini should fare well.

"It'svery exciting because it's something Cassini wasn't designed to do but shouldbe able to do safely," Stern said.

If theplanned flyby is approved within a few months, Stern explained that thespacecraft's more delicate instruments will be pointed away from the icyspray before entering the plume, leaving particle analyzers to sniff outits composition.

Greensaid NASA's Jet Propulsion Laboratory is currently analyzing the geyser's riskto Cassini and will submit a formal assessment before the end of the year.
"We want to be able to safely do science [with Cassini], but push thelimit," Green said.

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