CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Shadow and Streamer-Channels

The moon Prometheus casts a shadow on the thin F ring marked with streamer-channels created by the moon in this image taken as Saturn approaches its August 2009 equinox.

The gravity of potato-shaped Prometheus (86 kilometers, 53 miles across) periodically creates streamer-channels in the F ring. See PIA10461 and PIA10593 to learn more. To watch a movie of this process, see PIA08397.

The novel illumination geometry created as Saturn approaches its August 2009 equinox allows moons orbiting in or near the plane of Saturn's equatorial rings to cast shadows onto the rings. These scenes are possible only during the few months before and after Saturn's equinox which occurs only once in about 15 Earth years. To learn more about this special time and to see movies of moons' shadows moving across the rings, see PIA11651 and PIA11660.

This view looks toward the unilluminated side of the rings from about 52 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 15, 2009. The view was acquired at a distance of approximately 1.8 million kilometers (1.1 million miles) from Prometheus and at a Sun-Prometheus-spacecraft, or phase, angle of 85 degrees. Image scale is 11 kilometers (7 miles) per pixel.

The Cassini Equinox 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 Equinox Mission visit, and

Credit: NASA/JPL/Space Science Institute
Released: August 7, 2009 (PIA 11553)
Image/Caption Information
  Shadow and Streamer-Channels
PIA 11553

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Alliance Member Comments
Red_dragon (Aug 7, 2009 at 8:27 AM):
Excellent combination of streamers and Prometheus' shadow. If one does not look closely, even seems the shadow is warped.
stowaway (Aug 7, 2009 at 8:03 AM):
very cool ;-)