[meteorite-list] NASA Finds Saturn's Moons May Be Creating New Rings

[Ron Baalke]

Oct. 11, 2006

Dwayne Brown/Erica Hupp
Headquarters, Washington
202-358-1726/1237

Carolina Martinez
Jet Propulsion Laboratory
818-354-9382

RELEASE: 06-333

NASA FINDS SATURN'S MOONS MAY BE CREATING NEW RINGS

Cassini scientists are on the trail of the missing moons of Saturn. A 
recent observation by the spacecraft leads them to believe that they 
will find the moons near newly discovered rings around the planet.

During an unprecedented opportunity, with the sun poised behind 
Saturn, Cassini scientists discovered two new rings and confirmed the 
presence of two others. The new rings are associated with one or more 
small moons and share their orbits with the moons, while scientists 
suspect a moon is lurking near a third ring.

"Just like the old maxim that says where there's smoke, there's fire, 
at Saturn, where there's a new ring, there's bound to be a moon," 
said Jeff Cuzzi, Cassini interdisciplinary scientist at NASA's Ames 
Research Center, Moffett Field, Calif.

Under the cover of Saturn's shadow in mid-September, the entire ring 
system became visible, and never-before-seen microscopic particles 
began to appear. A single, faint new ring at the orbits of two 
moonlets, Janus and Epimetheus, was discovered. A second ring was 
found a week later. It is narrow and overlies the orbit of the tiny 
moon Pallene, which Cassini discovered back in 2004. A third and 
fourth ring are visible in the Cassini Division, the big gap in 
Saturn's main ring system. Curiously, these rings were not seen in 
images from NASA's Voyager spacecraft.

"We are hot on the trail of these possible elusive moonlets," said Joe 
Burn, Cassini imaging scientist at Cornell University, Ithaca, N.Y. 
"Finding the moons and learning about their interactions with the 
rings will help us understand how the moons formed and perhaps how 
the Saturn system formed."

When viewed by Cassini's infrared instrument, one of the rings in the 
Cassini Division has unusual coloring and brightening, a trait it 
shares with fresh, faint rings like the F ring, or those in the Encke 
Gap in Saturn's outer A ring.

Saturn's smallest moons have weak gravity and cannot retain any loose 
material on their surfaces. When these moons are struck by rapidly 
moving interplanetary meteoroids, this loose material is blasted off 
their surfaces and into Saturn orbit, creating diffuse rings along 
the moons' orbital paths. Collisions among several moonlets, or 
clumps of boulder-sized rubble, might also lead to debris trails. For 
instance, Saturn's G ring seems not to have any single moon large 
enough to see; it might have formed from a recent breakup of a moon.

The unusual viewing geometry provided other insights into the changing 
nature of Saturn's rings. In addition to the dazzling images, data 
from Cassini's visual and infrared mapping spectrometer also show 
distinct color differences, indicating variations in composition and 
in microscopic particles in the Cassini Division, the diffuse E- and 
G-rings, lying outside the main rings, and the D ring, which is the 
ring closest to Saturn.

"These tiny grains are like spices -- even a little bit of material 
can alter the ring's character," said Matt Hedman, another Cassini 
scientist at Cornell. Color variation in the rings might imply 
particles are being sorted by size.

"We expected to see things we haven't seen before, but we are really, 
really puzzled by these new images of Saturn's main ring system," 
said Phil Nicholson, of Cornell, Cassini visual and infrared 
spectrometer team member. "The rings appear very different, with none 
of their usual calling card of water-ice features. There are hints 
that other material besides ice might finally be detected within the 
rings."

"The main rings show a neutral color, while the C ring is reddish, and 
the D and E rings are quite blue," added Nicholson. "We don't quite 
understand if these variations are due to differences in particle 
size or composition, but it's nice to be surprised every once in a 
while."

Images to support this release, including an infrared mosaic and 
visible light mosaic of Saturn can be found at:

http://www.nasa.gov/cassini

The Cassini-Huygens mission is a cooperative project of NASA, the 
European Space Agency and the Italian Space Agency. The Jet 
Propulsion Laboratory, Pasadena, Calif., manages the Cassini-Huygens 
mission for NASA.

	
-end-