CICLOPS: Cassini Imaging Central Laboratory for OPerationS

The Ringsmith
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Prometheus tugs icy particles from the F ring into fanciful shapes like ropes of glowing neon.

Although Prometheus (86 kilometers, 53 miles across) is overexposed here, the moon's irregular outline is quite easy to see.

This view looks toward the sunlit side of the rings from about 7 degrees below the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 22, 2008. The view was obtained at a distance of approximately 1 million kilometers (652,000 miles) from Saturn. Image scale is 6 kilometers (4 miles) 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 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 and the Cassini imaging team home page,

Credit: NASA/JPL/Space Science Institute
Released: May 26, 2008 (PIA 09909)
Image/Caption Information
  The Ringsmith
PIA 09909

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Alliance Member Comments
Harry (May 30, 2008 at 6:14 PM):
Carolyn, Awesome film clip of Prometheus "perturbing" the F ring. I understand more now. I suppose the diffuse inner radius of the F ring could be from the periodic interactions with Prometheus. The slight eccentric orbit keeps the F ring from being having a more well defined inner radius. Thanks so much for the explanation.
carolyn (CICLOPS) (May 29, 2008 at 8:35 PM):
In order to understand phenomena like this, you must always remember that the dominant gravitational `perturber' in the system is Saturn. So Saturn's influence dominates over Prometheus' influence on the ring particles until Prometheus is practically on top of the ring particles. This is why you can get such counter-intuitive effects like a moon, like Pan or Daphnis, keeping a gap *open* instead of attracting all the nearby ring material onto itself. Also remember that the material in the F ring is orbiting slower than Prometheus. So once Prometheus makes a disturbance in the ring material, those particles that have been perturbed will travel slower and fall behind Prometheus. We have a nice movie posted on the CICLOPS site that follows the motion of Prometheus and shows how it affects the ring material only when, in its eccentric orbit, it comes close to the ring material. It is at . Enjoy!
Harry (May 29, 2008 at 6:54 PM):
Pictures like this confirm how little I understand about the gravitational/angular momentum balance that the rings represent. How can the inner strand of the F-ring shown keep from being disbursed by Prometheus? I presume these interactions are being modeled. Are there any papers published that explain how this happens? I enjoy a good set of equations probably more than most. But, if there are any, an intuitive explanatory paper that a layman such as myself could understand would be appreciated. My mind's "gut" does not understand how the strand shown does not eventually get disbursed by Prometheus. I presume the "rope loops" follow Prometheus radially like a tide. If so, why is there another loop behind Prometheus? Are they not in the same orbital plane? Ring coherence is a fact clearly established by the photo. With such extreme disturbance, it seem probable that collisions in the strand would eventually disburse the strand yet it does not; a mystery. Why does the asteroid belt not show the same behavior? Mars and Jupiter should create resonances there too. Maybe it does and I am naive. More photos and more questions... It is just great.

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