News Release: 2006-110 September 19, 2006
Scientists Discover New Ring and Other Features at Saturn
Saturn sports a new ring in an image taken by NASA's Cassini spacecraft
on Sunday,
Sept. 17, during a one-of-a-kind observation.
Other spectacular sights captured by Cassini's cameras include wispy
fingers of icy
material stretching out tens of thousands of kilometers from the active
moon, Enceladus,
and a cameo color appearance by planet Earth.
The images were obtained during the longest solar occultation of
Cassini's four-year
mission. During a solar occultation, the sun passes directly behind
Saturn, and Cassini
lies in the shadow of Saturn while the rings are brilliantly backlit.
Usually, an occultation
lasts only about an hour, but this time it was a 12-hour marathon.
Sunday's occultation allowed Cassini to map the presence of microscopic
particles that
are not normally visible across the ring system. As a result, Cassini
saw the entire inner
Saturnian system in a new light.
The new ring is a tenuous feature, visible outside the brighter main
rings of Saturn and
inside the G and E rings, and coincides with the orbits of Saturn's
moons Janus and
Epimetheus. Scientists expected that meteoroid impacts on Janus and
Epimetheus might
kick particles off the moons' surfaces and inject them into Saturn
orbit, but they were
surprised that a well-defined ring structure exists at this location.
Saturn's extensive, diffuse E ring, the outermost ring, had previously
been imaged one
small section at a time. The 12-hour marathon enabled scientists to
see the entire
structure in one view. The moon Enceladus is seen sweeping through the
E ring,
extending wispy, fingerlike projections into the ring. These very
likely consist of tiny ice
particles being ejected from Enceladus' south polar geysers, and
entering the E-ring.
"Both the new ring and the unexpected structures in the E ring should
provide us with
important insights into how moons can both release small particles and
sculpt their local
environments," said Matt Hedman, a research associate working with team
member
Joseph Burns, an expert in diffuse rings, at Cornell University in
Ithaca, N.Y.
In the latest observations, scientists once again see the bright
ghost-like spokes --
transient, dusty, radial structures -- streaking across the middle of
Saturn's main rings.
Capping off the new batch of observations, Cassini cast its powerful
eyes in our direction
and captured Earth, a pale blue orb, and a faint suggestion of our
moon. Not since
NASA's Voyager 1 spacecraft saw Earth as a pale blue dot from beyond
the orbit of
Neptune has Earth been imaged in color from the outer solar system.
"Nothing has greater power to alter our perspective of ourselves and
our place in the
cosmos than these images of Earth we collect from faraway places like
Saturn," said
Carolyn Porco, Cassini imaging team leader at the Space Science
Institute, Boulder,
Colo. Porco was one of the Voyager imaging scientists involved in
taking the Voyager
`Pale Blue Dot' image. "In the end, the ever-widening view of our own
little planet
against the immensity of space is perhaps the greatest legacy of all
our interplanetary
travels."
In the coming weeks, several science teams will analyze data collected
by Cassini's other
instruments during this rare occultation event. The data will help
scientists better
understand the relationship between the rings and moons, and will give
mission planners
a clearer picture of ring hazards to avoid during future ring
crossings.
Images of the new ring, the E-ring, Enceladus and Earth are available
at:
www.nasa.gov/cassini
,
saturn.jpl.nasa.gov
and
ciclops.org
.
Deirdre Kelleghan
Saturn Observation Campaign
saturn.jpl.nasa.gov/home/index.cfm
  