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Scientists
Discover New Ring and Other Features at Saturn
09.19.06
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.
A
new diffuse ring, coincident with the orbits of Saturn’s
moon’s Janus and Epimetheus, has been revealed in
ultra-high phase angle views from Cassini. Imgae credit:
NASA/JPL/Space Science Institute
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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 in the Scientific
Frontline Cassini Gallery
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. The Cassini
orbiter and its two onboard cameras were designed, developed and
assembled at JPL. The imaging team is based at the Space Science
Institute, Boulder, Colo.
Source / Credit: NASA /
JPL
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