Spacecraft Cassini plans two flybys of Saturn's geyser moon in October
7/10/2008 16:06
Spacecraft Cassini will fly by Saturn's geyser moon, Enceladus, twice in
October, the US space agency NASA reported yesterday.
The Oct. 9 flyby is an
inside pitch -- the closest flyby yet of any moon of Saturn, at only 25 km from
the surface. The Oct. 31 flyby is farther out, at 196 km.
The Enceladus
geysers were discovered by Cassini in 2005. It produces a few hundred kg per
second of gas and dust, which are mainly water vapor and water ice.
Since
then, scientists have been intrigued about what powers them, because the moon is
so tiny, at only 500 km in diameter.
Scientists are intrigued by the
possibility that liquid water, perhaps even an ocean, may exist beneath the
surface of Enceladus. Trace amounts of organics have also been detected, raising
tantalizing possibilities about the moon's habitability.
During Cassini's
Oct. 9 flyby, the spacecraft's fields and particles instruments will venture
deeper into the plume than ever before, directly sampling the particles and
gases.
"One of the overarching scientific puzzles we are trying to understand
is what happens to the gas and dust released from Enceladus, including how some
of the gas is transformed to ionized plasma and is disseminated throughout the
magnetosphere," said Tamas Gambosi, Cassini scientist at University of
Michigan.
On Oct. 31, cameras and other optical remote sensing instruments
will be front and center, imaging the fractures that slash across the moon's
south polar region like stripes on a tiger.
These two flybys might augment
findings from the most recent Enceladus flyby on Aug. 11, 2008, which hint at
possible changes associated with the icy moon.
Results from Cassini's
magnetometer instrument during the August flyby suggest a difference in the
intensity of the plume compared to earlier encounters. Information from the next
two flybys will help scientists understand these observations.
Cassini has
been orbiting Saturn since 2004. Four more Enceladus flybys are planned in the
next two years, according to NASA's mission schedule.
Xinhua
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