Methane Found on Saturn Plays Crucial Role in Planet Formation

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Lawrence Livermore National Laboraty
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FOR IMMEDIATE RELEASE
December 23, 2004
NR-04-12-08

Methane found on Saturn plays crucial role in planet formation

LIVERMORE, Calif. - Using an infrared spectrometer on the
Cassini-Huygens Spacecraft, researchers have measured the temperature,
winds and chemical composition of Saturn, its rings and one of its
moons, Phoebe.

The data appears in the Dec. 23 edition of "Science Express" and in
the
Dec. 24 print edition of Science.

Edward Wishnow of Lawrence Livermore National Laboratory participated
in
the research by measuring the spectrum of methane in the laboratory at
temperatures and densities similar to the planet's - about 90 Kelvin
(-297
degrees F) and one atmosphere of pressure. Methane (CH4), the principal
component of natural gas, is the main indicator of carbon on Saturn and
Jupiter, and it plays a crucial role in the planet's atmospheric
chemistry and history of formation.

The Cassini Composite Infrared Spectrometer (CIRS) is an infrared
instrument that measures the intensity of far-infrared radiation, light
with wavelengths between those of radar and near-infrared light. These
wavelengths are associated with radiation emission by the constituent
gases of the planet?s atmosphere or the ices and/or rocks that
compose
the rings and the moon Phoebe.

"Though we've known for years that the atmospheres of the giant planets
are mainly made up of hydrogen and helium, using these instruments, we
were able to measure the methane content with much greater precision
than previous space missions," said Wishnow, who works in LLNL?s
Physics
and Advanced Technologies Directorate.

The methane measurement shows that carbon is enriched on Saturn by
seven
times the amount found in the sun and two times the amount found on
Jupiter, which is consistent with the rocky core hypothesis of giant
planet formation. In this model, Jupiter and Saturn began formation by
accreting cores of about 10-12 times the size of Earth?s mass of
heavy
elements, which, in turn, attracts the surrounding nebular gas in solar
proportions.

Wishnow's laboratory work was conducted with collaborators at the
University of British Columbia and was supported by a NASA planetary
atmospheres grant.

Other collaborators on the CIRS project include scientists from
NASA/Goddard Space Flight Center, the Jet Propulsion Laboratory and
French and British institutions.

Cassini was launched in July 2004 with a mission to orbit around Saturn
and its moons for the next four years. The Huygens probe is scheduled
to
enter the atmosphere of Titan, Saturn?s biggest moon, on Jan. 14, and
eventually descend on a parachute onto its surface about 2? hours
later.
Huygens will send its measurements and images to Cassini, which will
then send them back to Earth.

Founded in 1952, Lawrence Livermore National Laboratory has a mission
to
ensure national security and to apply science and technology to the
important issues of our time. Lawrence Livermore National Laboratory is
managed by the University of California for the U.S. Department of
Energy's National Nuclear Security Administration.