CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Pan's Lengthening Shadow

Saturn's moon Pan casts a longer shadow across the A ring as the planet's August 2009 equinox draws near.

For an earlier image showing a shorter shadow, see PIA11652.

The novel illumination geometry created around the time of Saturn's 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.

Pan (28 kilometers, 17 miles across) orbits in the Encke Gap. This view looks toward the unilluminated side of the rings from about 34 above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 27, 2009. The view was acquired at a distance of approximately 839,000 kilometers (522,000 miles) from Pan and at a Sun-Pan-spacecraft, or phase, angle of 74 degrees. Image scale is 5 kilometers (3 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 16, 2009 (PIA 11581)
Image/Caption Information
  Pan's Lengthening Shadow
PIA 11581

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Alliance Member Comments
carolyn (CICLOPS) (Sep 17, 2009 at 11:40 AM):
Dragon: The bright ringlet looks different because it is in fact a bending wave, and sticks out above the ring plane. If you look closely, you'll see that the shadow takes a jog there, just like you would expect if it were cast over a vertical protrusion.
Dragon_of_Luck_Mah_Jonng1971 (Sep 17, 2009 at 10:09 AM):
The bright ringlet at the right seems to be a bit thicker because there the moonlet's shadow looks a bit different.