CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Moons at Work
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The ring-region Saturnian moons Prometheus and Pan are both caught "herding" their respective rings in this image. Through their gravitational disturbances of nearby ring particles, one moon maintains a gap in the outer A ring and the other helps keep a ring narrowly confined.

Prometheus (53 miles, 86 kilometers across), together with Pandora, maintains the narrow F ring seen in this image, and Pan (17 miles, 28 kilometers across) holds open the Encke gap in which it finds itself embedded. The bright dot near the inner edge of the Encke gap is a background star.

This view looks toward the unilluminated side of the rings from about 29 degrees below the ringplane. The image was taken in visible violet light with the Cassini spacecraft narrow-angle camera on Sept. 18, 2012.

The view was acquired at a distance of approximately 1.4 million miles (2.3 million kilometers) from Pan and at a Sun-Pan-spacecraft, or phase, angle of 98 degrees. Image scale is 8 miles (14 kilometers) per pixel.

The Cassini Solstice Mission is a joint United States and European endeavor. 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 was designed, developed and assembled at JPL. 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 Solstice Mission visit, and

Credit: NASA/JPL-Caltech/Space Science Institute
Released: January 21, 2013 (PIA 14644)
Image/Caption Information
  Moons at Work
PIA 14644

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Alliance Member Comments
NeKto (Jan 27, 2013 at 7:03 AM):
i continue to be astounded by the detail in the images that keep on coming. the only words i can find that express my understanding, and lack thereof to the movement in the rings is there is a complex simplicity to the dynamics of the ring particles. then again, i was momentarily fooled by that other "moon" in this image. (the one identified as "background star") first look i was trying to remember what other moon was in the Encke gap. then i had the thought "background star" is a very unusual name for a moon.

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