CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Crescent at Equinox

Cassini looks down and pictures Saturn wrapped in a pencil-thin shadow of the rings just days after the planet's August 2009 equinox.

The moon Epimetheus is not shown here, but it is casting a tiny shadow on the planet above the rings. The moon Enceladus (504 kilometers, 313 miles across) is faintly visible in the far top right of the image.

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 13 degrees above the ringplane. The rings have been brightened by a factor of 10 relative to the planet.

The image was taken with the Cassini spacecraft wide-angle camera on Aug. 17, 2009 using a spectral filter sensitive to wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 2.2 million kilometers (1.4 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 109 degrees. Image scale is 125 kilometers (78 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: April 30, 2010 (PIA 12623)
Image/Caption Information
  Crescent at Equinox
PIA 12623

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