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Cassini reveals a remarkable amount of structure in the outer portion of Saturn's A ring.
The granular look of the outer edge of the A ring, first discovered soon after Cassini's orbit insertion, is likely created by gravitational clumping of particles there. As ring particles round the planet in their orbits in this region, they also become perturbed by the gravitational forcing of Saturn's two moons, Janus and Epimetheus, whose gravitational resonance at the A ring's outer edge periodically forces the particles close together, promoting clumping (see PIA09892). Similar clumping is seen at the outer edge of the B ring where a resonance with Mimas has a similar effect on the ring particle orbits (see PIA10421).
The view was obtained at a distance of approximately 206,000 kilometers (128,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 108 degrees. This view looks toward the sunlit side of the rings from about 64 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 2, 2008. Image scale is 901 meters (2,954 feet) per pixel.
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, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.