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International Scientists Discover New Ring at Saturn

20 September 2006

Cassini also captured "pale blue dot" of Earth and faint image of moon

Washington – A newly discovered ring of Saturn was captured in an image taken by NASA's Cassini spacecraft September 17 during a one-of-a-kind observation.

Other spectacular sights photographed by Cassini's cameras include wispy fingers of icy material stretching tens of thousands of kilometers from the active moon, Enceladus, and a color image of planet Earth, according to a September 19 press release from the NASA Jet Propulsion Laboratory (JPL) in California.

The images were taken 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 event.

The most recent occultation allowed Cassini to map the presence of microscopic particles that are not normally visible across the ring system. As a result, Cassini captured the entire inner Saturnian system in a new light.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and Agenzia Spaziale Italiana, the Italian space agency.

NEW SATURN RING

The new ring is a tenuous feature, visible outside the brighter main rings of Saturn and inside the G and E rings. It coincides with the orbits of Saturn's moons Janus and Epimetheus.

Scientists had expected that meteoroid impacts on Janus and Epimetheus might kick particles off the moons' surfaces and inject them into Saturn’s orbit, but they were surprised that a well-defined ring structure exists at this location.

Saturn's extensive, diffuse E ring, the outermost ring, previously had been imaged one small section at a time. The 12-hour occultation let scientists see the entire structure in one view.

In the photographs, 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.

"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 New York.

In the latest observations, scientists once again can see the bright ghost-like spokes -- transient, dusty, radial structures -- streaking across the middle of Saturn's main rings.

AN EYE TOWARD EARTH

Capping off the new batch of observations, Cassini cast its powerful lenses in Earth’s direction and captured the pale blue orb and a faint suggestion of the 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 in Colorado.

Porco was one of the Voyager imaging scientists involved in taking the “Pale Blue Dot” image.

"In the end,” she said, “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. Those 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 on NASA Web sites.

The full text of the press release is available on the JPL Web site.

(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)