CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Moons that Share
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The two moons pictured here each share their orbits with other bodies.

Dione (1,123 kilometers, 698 miles across, at left) has two much smaller "Trojan" moons, Helene and Polydeuces, that orbit 60 degrees in front of and behind it in its orbit. Epimetheus (113 kilometers, 70 miles across) shares its orbital path with Janus, and the two moons swap positions every few years--one moving just a bit closer to Saturn and the other moving slightly farther away.

This view looks toward the unilluminated side of the rings from less than a degree above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 28, 2007. Cassini was approximately 2.9 million kilometers (1.8 million miles) from Saturn when it acquired this view. Image scale is 15 kilometers (9 miles) per pixel on Dione.

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: September 19, 2007 (PIA 09731)
Image/Caption Information
  Moons that Share
PIA 09731

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