NASA's Cassini Spacecraft Continues Making New Saturn Discoveries
NASA's Cassini spacecraft continues making new and exciting
discoveries. New findings include wandering and rubble-pile
moons; new and clumpy Saturn rings; splintering storms and a
"For the last seven months it has been a nonstop, science-packed
mission. It has been a whirlwind, and already we have many new
results," said Dr. Dennis Matson, Cassini project scientist at
NASA's Jet Propulsion Laboratory, Pasadena, Calif.
Image right: Saturn's atmosphere and its rings are shown here in a false color composite made from Cassini images taken in near infrared light through filters that sense different amounts of methane gas. Image credit: NASA/JPL/Space Science Institute.
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Weak, linear density waves caused in Saturn's rings by the small
moons Atlas and Pan have yielded more reliable calculations of
their masses. The masses imply the moons are very porous, perhaps
constructed like rubble piles. They are similar to the moons that
shepherd Saturn's F ring, Prometheus and Pandora.
Another discovery was a tiny moon, about 5 kilometers (3 miles)
across, recently named Polydeuces. Polydeuces is a companion, or
"Trojan" moon of Dione. Trojan moons are found near
gravitationally stable points ahead or behind a larger moon.
Saturn is the only planet known to have moons with companion
Image above: In early October 2004, Cassini captured a series of images that have been composed into the largest, most detailed, global natural color view of Saturn and its rings ever made. Image credit: NASA/JPL/Space Science Institute.
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The new findings, published in this week's edition of the journal
Science, include refinements in the orbits of several of Saturn's
small satellites. One intriguing result is the eccentric and
slightly inclined orbit of Pan in Saturn's A ring. The orbit's
shape is significant, as it indicates the type of interaction the
moon has with the ring material surrounding it. If Pan's orbit
remains eccentric due to this interaction, then planets growing
in a disc of material surrounding a star may also have eccentric
orbits. This may help explain the eccentric paths of planets
orbiting other stars.
Several faint Saturn rings have been discovered in Cassini
images. Some lie in various gaps in the rings and may indicate
the presence of tiny embedded moons acting as shepherds. Several
of the rings are kinked, likely evidence of nearby moons.
Scientists also found Saturn's winds change with altitude, and
small storms emerge out of large ones. For the first time,
Cassini images captured possible evidence of processes that may
maintain the winds on Saturn. The observations offer a glimpse
into the process which transfers energy by convection from
Saturn's interior to help sustain strong winds.
Other results improve the understanding of Saturn's complex
magnetic environment. "Saturn's magnetosphere is truly unique.
It's dynamically similar to Jupiter's, but in places it
chemically resembles water-based plasmas surrounding comets,"
said Dr. David Young. Young is Cassini principal investigator for
the plasma spectrometer instrument from the Southwest Research
Institute, San Antonio.
Another surprising find was made by the ion and neutral mass
spectrometer instrument, which measured molecular oxygen ions
above Saturn's ring plane. "This is at first surprising since the
rings are made of water ice," said Dr. Hunter Waite, principal
investigator for the spectrometer from the University of
Michigan, Ann Arbor. "This may have important consequences for
the identification of spectral features to use in the search for
life on extrasolar terrestrial planet systems."
The abundance of molecular oxygen on Earth is uniquely tied to
biology. But these new measurements at Saturn suggest there are
lifeless processes associated with cold icy surfaces that may
produce an independent pathway for the formation of molecular
oxygen in atmospheres.
For images and information on the Cassini mission visit
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 Science Mission Directorate, Washington, D.C. The Cassini
orbiter was designed, developed and assembled at JPL.
Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.
Dolores Beasley (202) 358-1753
NASA Headquarters, Washington