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 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 (2,960 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.
For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov/. The Cassini imaging team
homepage is at http://ciclops.org.
