The Cassini
spacecraft will perform its closest flyby ever of Saturn's ice-spewing moon
Enceladus early next year, moving directly into its icy polar geyser for a deep-space
shower.
Cassini's third flyby of Enceladus (en-SELL-ah-dus), set for
March 2008, will swing it within 19 miles (30 kilometers) of the saturnian moon—almost
six times closer than the spacecraft's closest pass to it in 2005. The tight
trajectory will move Cassini directly into the icy
geyser at the moon's southern pole, said NASA official James Green during a
teleconference today.
"Cassini was never designed to fly
this close, but we've just got to get in that plume and look at that material
and see what it is and where it's coming from," said Green, director of NASA's Planetary Division in Washington,
D.C.
Scientists think
the geyser is 90 percent fine water-ice
crystals, but suspect ammonia and methane gas are present as well.
Although
the flyby isn't without risk, Alan Stern, associate administrator for NASA's
Science Mission Directorate in Washington, D.C., said Cassini should fare well.
"It's
very exciting because it's something Cassini wasn't designed to do but should
be able to do safely," Stern said.
If the
planned flyby is approved within a few months, Stern explained that the
spacecraft's more delicate instruments will be pointed away from the icy
spray before entering the plume, leaving particle analyzers to sniff out
its composition.
Green
said NASA's Jet Propulsion Laboratory is currently analyzing the geyser's risk
to 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 the
limit," Green said.
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