English: This movie sequence from Cassini shows dark drapes in the inner strands of the F ring caused by the gravitational influence of the shepherd moon Prometheus (102 kilometers, 63 miles across).

Prometheus appears first in the sequence, interior to the F ring, and Pandora (84 kilometers, 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 comes 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 due to differential orbital motion, create the dark, diagonal drapes.

Several background stars are seen moving across the field during the movie.

The visible light images in this sequence were acquired using the narrow angle camera on April 13, 2005 from a distance of approximately 1.2 million kilometers (700,000 miles) from Saturn.

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.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

This is a Theora video, at 2.5 frames per second, converted directly from NASA's full-size animated gif version of the sequence, using: gifsicle to unoptimize and then explode the original GIF into its component frames; ffmpeg2theora-0.25.exe to construct an OGG Theora video from those frames. The default quality option, --videoquality 10, (1 is lowest, 10 is best) was used for this video.

The full size image sequence is also available at http://photojournal.jpl.nasa.gov/animation/PIA07712. 2005-04-13 (original), 2009-10-18 (OGV creation)