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Planetary News: Cassini-Huygens (2006)

Cassini Discovers New Ring at Saturn and Looks Back at Our Pale Blue Earth

 

September 20, 2006
A new Ring
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A new Ring
On September 15, 2006, Cassini revealed a new diffuse ring at Saturn, coincident with the orbits of Janus and Epimetheus. This observation occurred during a solar occultation, where the Sun passed directly behind Saturn and left Cassini in Saturn's shadow with brilliantly backlit rings. Usually, an occultation lasts only about an hour, but this time it was an unusual 12-hour marathon.

The new ring is marked by a cross in the inset of the image just outside the overexposed main rings and interior to the G and E rings. The G ring has a sharp inner boundary; the E ring is extremely broad and arcs across the upper and lower portions of the scene. Credit: NASA / JPL / Space Science Institute

During a rare observation last weekend, Cassini's cameras revealed a new ring at Saturn and other spectacular sights, including wispy fingers of icy material stretching out tens of thousands of kilometers from Enceladus and even an image of distant planet Earth.

Cassini captured these images during a solar occultation -- the Sun passed directly behind Saturn, leaving Cassini in Saturn's shadow with brilliantly backlit rings. Usually, an occultation lasts only about an hour, but this time it was a 12-hour marathon.

The 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.  But, because of the unusual 12-hour occultation, scientists were able to see the entire structure in one view. In the image, Enceladus sweeps through the E ring, extending wispy, fingerlike projections into the ring. These very likely consist of tiny ice particles that Enceladus' south polar geysers ejected and entered 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, New York.

In addition to these new views of Saturn, scientists once again see the bright ghost-like spokes -- transient, dusty, radial structures -- streaking across the middle of Saturn's main rings.

Cassini Captures a View of 'Home'
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Cassini Captures a View of "Home"
Cassini casts powerful eyes on our home planet, and captures the pale blue orb of our Earth -- and a faint suggestion of our Moon -- among the glories of the Saturn system. The Earth-Moon system is visible as a bright blue point on the right side of the image above center. Here, Cassini is looking down on the Atlantic Ocean and the western coast of north Africa. NASA / JPL / Space Science Institute

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. 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."

Images of the new ring, the E-ring, Enceladus and Earth are available at JPL's Cassini Site and at the CICLOPS site.