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The Black Spot | by Planetary Ring Image of the Day
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The Black Spot


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 10 to 100 meters (30 to 300 feet) thick for the

most part, 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



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-Huygens mission is a cooperative project of NASA, the European

Space Agency and the Italian Space Agency. 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 and its two onboard cameras were designed, developed and

assembled at JPL. The imaging operations center is based at the Space

Science Institute in Boulder, Colo.


For more information about the Cassini-Huygens mission visit The Cassini imaging team

homepage is at NASA/JPL/Space Science Institute


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Taken on April 30, 2012