CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Long Shadow, Short Shadow

The shadow of the moon Janus dwarfs the shadow of Daphnis on Saturn's A ring in this image taken as the planet approached its August 2009 equinox.

Daphnis (8 kilometers, 5 miles across) orbits in the A ring's Keeler Gap and, along with the moon's attending edge waves, can be seen casting a short shadow in the top left quadrant of the image. Equinox has exposed shadows cast by these edge waves, or vertical structures of ring material created by Daphnis' gravity (see PIA11655).

Janus (179 kilometers, 111 miles across) is not pictured here, but the moon's shadow stretches across the A ring from the center of the image to near the Encke Gap on the left of the image. The Cassini Division appears bright on the right of the image.

The novel illumination geometry created around the time of Saturn's August 2009 equinox allows out-of-plane structures and 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 27 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft wide-angle camera on July 11, 2009. The view was obtained at a distance of approximately 491,000 kilometers (305,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 26 degrees. Image scale is 26 kilometers (16 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: September 4, 2009 (PIA 11573)
Image/Caption Information
  Long Shadow, Short Shadow
PIA 11573

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Alliance Member Comments
stowaway (Sep 4, 2009 at 11:56 AM):
Nice, very nice. This one really conveys a feeling of "being there".