This movie sequence from Cassini shows dark drapes in the inner strands of Saturn's F ring caused by the gravitational influence of the shepherd moon Prometheus (102 kilometers, or 63 miles across).
Prometheus appears first in the sequence, interior to the F ring, and Pandora (84 kilometers, or 52 miles across) follows along outside of the ring. Radial structure in the bright core of the ring is visible throughout the movie.
Prometheus orbits closer to Saturn, and thus faster, than the icy particles that make up the F ring. The moon passes closest to the ring at "apoapse", when it is farthest from Saturn. It is during these apoapse passages that Prometheus has its greatest influence on the fine ring material. With time, the ring material previously affected falls behind so that on the next apoapse passage of Prometheus, a new gore in the inner ring material is made. The material closer to Prometheus orbits the planet faster than the material closer to the bright F ring core. The gores, together with the sheared-out material, create the dark, diagonal drapes.
Several background stars are seen moving across the field during the movie.
The images in this sequence were acquired on April 13, 2005, at a distance of approximately 1.2 million kilometers (700,000 miles) from Saturn. The images were obtained in visible light using the Cassini spacecraft narrow-angle camera.
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 .
Credit: NASA/JPL/Space Science Institute