CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Round the Outside
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The moon Pan casts a shadow on Saturn's outer A ring in this image taken as the planet approached its August 2009 equinox.

Pan (28 kilometers, 17 miles across) orbits in the Encke Gap of the A ring, and its shadow has been imaged several times by Cassini cast in the direction of the interior of the A ring (see PIA11652 and PIA11549). In this image, the shadow is cast in the opposite direction.

The novel illumination geometry that accompanies equinox lowers the sun's angle to the ringplane, significantly darkens the rings, and causes out-of-plane structures to look anomalously bright and cast shadows across 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. Before and after equinox, Cassini's cameras have spotted not only the predictable shadows of some of Saturn's moons (see PIA11657), but also the shadows of newly revealed vertical structures in the rings themselves (see PIA11665).

This view looks toward the northern, unilluminated side of the rings from about 28 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 29, 2009. The view was acquired at a distance of approximately 1.6 million kilometers (994,000 miles) from Pan. Image scale is 9 kilometers (6 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: October 6, 2009 (PIA 11595)
Image/Caption Information
  Round the Outside
PIA 11595

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