Cassini Exposes Puzzles About Ingredients In Saturn's Rings

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Carolina Martinez (818) 354-5011
Jet Propulsion Laboratory, Pasadena, Calif.

Donald Savage (202) 358-1727

NASA Headquarters, Washington

News Release: 2004-170 July 2, 2004

Cassini Exposes Puzzles About Ingredients In Saturn's Rings

Just two days after the Cassini spacecraft entered Saturn orbit,
preliminary science results are already beginning to show a complex
and fascinating planetary system.

One early result intriguing scientists concerns Saturn's Cassini
Division, the large gap between the A and B rings. While Saturn's
rings are almost exclusively composed of water ice, new findings show
the Cassini Division contains relatively more "dirt" than ice.
Further, the particles between the rings seem remarkably similar to
the dark material that scientists saw on Saturn's moon, Phoebe. These
dark particles refuel the theory that the rings might be the remnants
of a moon. The F ring was also found to contain more dirt.

Another instrument on Cassini has detected large quantities of oxygen
at the edge of the rings. Scientists are still trying to understand
these results, but they think the oxygen may be left over from a
collision that occurred as recently as January of this year.

"In just two days, our ideas about the rings have been expanded
tremendously," said Dr. Linda Spilker, of NASA's Jet Propulsion
Laboratory, Pasadena, Calif., deputy project scientist for the
Cassini-Huygens mission. "The Phoebe-like material is a big surprise.
What puzzles us is that the A and B rings are so clean and the Cassini
Division between them appears so dirty."

The visual and infrared mapping spectrometer onboard Cassini revealed
the dirt mixed with the ice in the Cassini Division and in other small
gaps in the rings, as well as in the F ring.

"The surprising fingerprint in the data is that the dirt appears
similar to what we saw at Phoebe. In the next several months we will
be looking for the origin of this material," said Dr. Roger Clark, of
the U.S. Geological Survey, Denver, Colo., and a member of the Cassini
science team.

Cassini's ultraviolet imaging instrument detected the sudden and
surprising increase in the amount of atomic oxygen at the edge of the
rings. The finding leads scientists to hypothesize that something may
have collided with the main rings, producing the excess oxygen.

Dr. Donald Shemansky of the University of Southern California, Los
Angeles, co-investigator for Cassini's ultraviolet imaging
spectrograph instrument, said, "What is surprising is the evidence of
a strong, sudden event during the observation period causing
substantial variation in the oxygen distribution and abundance."
Although atomic oxygen has not been previously observed, its presence
is not a surprise because hydroxyl was discovered earlier from Hubble
Space Telescope observations, and these chemicals are both products of
water chemistry.

Cassini's examination of Saturn's atmosphere began while the
spacecraft was still approaching the planet. Winds on Saturn near the
equator decrease dramatically with altitude above the cloud tops. The
winds fall off by as much 140 meters per second (approximately 300
miles per hour) over an altitude range of 300 kilometers
(approximately 200 miles) in the upper stratosphere. This is the first
time winds have been measured at altitudes so high in Saturn's
atmosphere.

"We are finally defining the wind field in three dimensions, and it is
very complex," said Dr. Michael Flasar of NASA Goddard Space Flight
Center, Greenbelt, Md., principal investigator for Cassini's composite
infrared spectrometer. "Temperature maps obtained now that Cassini is
orbiting Saturn are expected to show more detail, helping us to
unravel the riddles of Saturn's winds above the cloud tops."

Early Friday (Pacific Time), Cassini imaged Saturn's largest moon
Titan, one of the prime targets for the mission. Titan is thought to
harbor simple organic compounds that may be important in understanding
the chemical building blocks that led to life on Earth. Although too
cold to support life now, Titan serves as a frozen vault to see what
early Earth might have been like. Scientists will receive the new
data and images from Titan later Friday.

The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Jet Propulsion
Laboratory, a division of the California Institute of Technology in
Pasadena, manages the Cassini-Huygens mission for NASA's Office of
Space Science, Washington, D.C. JPL designed, developed and assembled
the Cassini orbiter.

For the latest images and more information about the Cassini-Huygens
mission, visit

http://saturn.jpl.nasa.gov

and

http://www.nasa.gov/cassini .

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