Although their gravitational effects on nearby ring material look quite different, Prometheus and Pan -- pictured here -- are both shepherd moons, holding back nearby ring edges.
Pan (17 miles,or 28 kilometers across), near the right edge of the image, holds open the Encke gap that it orbits in. Prometheus (53 miles, or 86 kilometers across), near the upper left, helps shape the F ring and maintain its narrow form.
This view looks toward the unilluminated side of the rings from about 47 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 27, 2013.
The view was acquired at a distance of approximately 870,000 miles (1.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 81 degrees. Image scale is 5 miles (8 kilometers) 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 and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org.