CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Streamer-Channels and Shadow
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Saturn's moon Prometheus, orbiting near the streamer-channels it has created in the thin F ring, casts a shadow on the A ring in this image taken a little more than a week after the planet's August 2009 equinox.

Potato-shaped Prometheus (86 kilometers, 53 miles across) periodically creates streamer-channels in the F ring, and the moon's handiwork can be seen on the left of the image. To learn more and to watch a movie of this process, see PIA08397.

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, sunlit side of the rings from about 8 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 21, 2009. The view was acquired at a distance of approximately 2.2 million kilometers (1.4 million miles) from Saturn. Image scale is 13 kilometers (8 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: November 25, 2009 (PIA 11631)
Image/Caption Information
  Streamer-Channels and Shadow
PIA 11631

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