||The Cassini spacecraft 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. The resulting gravitational resonance at the A ring's outer edge periodically forces the particles close together, promoting clumping (see Scrambled Edge). 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 Perturbed Edge).
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 (2,960 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 mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.