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
saturn.jpl.nasa.gov. The Cassini imaging team
homepage is at ciclops.org.credit: NASA/JPL/Space Science Institute
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