[meteorite-list] Cassini Finds More Rings Highlighed By Telltale Small Particles

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Oct 12 12:09:39 2006
Message-ID: <200610121609.JAA09783_at_zagami.jpl.nasa.gov>

http://ciclops.org/view.php?id=2282

MEDIA RELATIONS OFFICE
CASSINI IMAGING CENTRAL LABORATORY FOR OPERATIONS (CICLOPS)
SPACE SCIENCE INSTITUTE, BOULDER, COLORADO
http://ciclops.org
media_at_ciclops.org

Preston Dyches (720) 974-5859
CICLOPS/Space Science Institute, Boulder, Colo.

For Immediate Release: October 11, 2006

CASSINI FINDS MORE RINGS HIGHLIGHTED BY TELLTALE SMALL PARTICLES

Images taken by NASA's Cassini spacecraft, looking in the direction of
the Sun, have provided scientists fresh insights into the dynamic nature
of the rings and, in particular, the creation of new rings made from
tiny particles released from larger bodies.

Cassini findings being presented this week at the Division for Planetary
Sciences Meeting of the American Astronomical Society held in Pasadena,
Calif. include several new faint ring structures formed by processes
acting on and within Saturn's moons and main rings.

A series of unique observations gathered in mid-September by NASA's
Saturn-orbiting Cassini spacecraft as it drifted slowly through Saturn's
shadow, allowed the entire ring system to be seen from a perspective
that highlights microscopic ring particles: in many cases, particles
only recently released into Saturn orbit. While observing from this
locale, Cassini spotted, a single faint new ring, announced previously,
in the shared orbit of the moons Janus and Epimetheus.

Scientists are now ecstatic to find even more rings. A second new
diffuse but narrow ring is coincident with the orbit of the tiny moon
Pallene, also discovered by Cassini's imaging cameras and only 4
kilometers (2.5 miles) across. Curiously, another similar-sized moon
called Methone, discovered earlier in the mission in roughly the same
region, does not seem to sport a ring.

A third diffuse ring--the brightest seen in the Cassini Division between
the main A and B rings--was also spotted on Sept. 15 from Saturn's shadow.

Finally, a faint, very narrow, and seemingly discontinuous ringlet was
also found between the broad bands of ring material in the Cassini
Division. Though too small to be resolved during the September
observations, it too was first seen in images taken in a geometry that
enhances the visibility of small particles.

"Cassini's superior cameras and close orbits around Saturn allow us to
spot fainter and narrower rings than Voyager was able to see", said Dr.
Joseph Spitale, an imaging team associate working with team leader Dr.
Carolyn Porco. "I wouldn't be surprised if we find more as time goes on."

All of these new rings are likely formed and maintained by impacts onto
larger bodies, whether moons or large ring particles. These impacts
blast material off their surfaces, creating diffuse rings in the same
orbit as the parent body.

Saturn's diffuse rings are a subset that includes the E, G, and newly
discovered rings. Scientists suspect that the G ring is created by
impacts into bodies trapped in a remarkably bright arc in the ring.
Unlike the other diffuse rings, however, Cassini observations have
confirmed that the E ring is created by tiny ice particles spewing from
surface jets on the geologically active moon Enceladus.

No matter how they are released, small grains are pushed about by
sunlight and by electrical forces; hence their distribution tells much
about the local space environment.

Imaging scientists have also noticed color variations across the diffuse
rings that imply active processes sort the particles along the ring
according to their sizes. Looking at the faint rings on one side of
Saturn, the E ring appears to have a red core with a bluish halo, but
the appearance is reversed on the right side--where there is a blue ring
interior to a red ring.

According to Dr. Matt Hedman, an imaging team associate working at
Cornell University in Ithaca, NY, this color variation may imply
particles are being sorted by some process according to their sizes.

"These tiny grains are like spices--even a little bit of material can
alter the ring's character," Hedman said.

Additionally, Cassini acquired a movie sequence and other images showing
the narrowly confined G ring and its faint arc of material, which is
likely held in place by a gravitational resonance with one of Saturn's
moons.

Imaging Team member Joe Burns, also of Cornell University remarks,
"We've been stunned by the rings' variability. Who would have thought,
even a few years ago, that we'd see so many new features as the Cassini
mission progressed?"

Images accompanying this release, including the G ring movie and a full
color panoramic view of Saturn, are available at http://ciclops.org,
http://www.nasa.gov/cassini, and http://saturn.jpl.nasa.gov.

The Cassini-Huygens mission is a cooperative project of NASA, the
European Space Agency and the Italian Space Agency. The Jet Propulsion
Laboratory (JPL), a division of the California Institute of Technology
in Pasadena, manages the Cassini-Huygens mission for NASA's Science
Mission Directorate, Washington. The Cassini orbiter and its two onboard
cameras were designed, developed and assembled at JPL. The imaging team
consists of scientists from the U.S., England, France, and Germany. The
imaging operations center and team leader (Dr. C. Porco) are based at
the Space Science Institute in Boulder, Colo.

-end-
Received on Thu 12 Oct 2006 12:09:35 PM PDT