CICLOPS: Cassini Imaging Central Laboratory for OPerationS

The Black Spot
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A big shadow from Saturn's largest moon darkens the planet in the lower right of this image taken shortly after Saturn's August 2009 equinox.

Titan, the shadow caster, is not shown. The planet is overexposed in this image because the camera's long exposure time was set to show the rings which are dimly lit at equinox. The transparent D ring, which stretches from the middle of the image to the left, is not visible, but the C ring can be seen in the upper left of the image. The excess brightness in the middle of the image is lens flare, an artifact resulting from light being scattered within the camera optics.

Saturn's rings, which are vertically very thin, cast a narrow shadow onto the planet.

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 11 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 19, 2009. The view was obtained at a distance of approximately 2.3 million kilometers (1.4 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 116 degrees. 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 http://ciclops.org, http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

Credit: NASA/JPL/Space Science Institute
Released: September 22, 2009 (PIA 11585)
Image/Caption Information
  The Black Spot
PIA 11585

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Alliance Member Comments
Red_dragon (Sep 22, 2009 at 8:02 AM):
It's a pity that: 1) Titan's shadow is so off-center and 2) not to have caught it when Cassini was in front of the planet. Anyway, good work!. This is what we were waiting for since the Equinox mission was announced.

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