The Cassini spacecraft snags a close-up view of the shadow cast onto
Saturn's A ring by the moon Epimetheus as the planet approached its August
2009 equinox.
Epimetheus (113 kilometers, or 70 miles across) is not pictured here. See
PIA11651 for an earlier, wide-angle-camera view which showed a short
shadow from Epimetheus.
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, unilluminated side of the rings from
about 19 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow
angle camera on July 11, 2009. The view was obtained at a distance of
approximately 447,000 kilometers (278,000 miles) from Saturn. Image scale
is 2 kilometers (1 mile) 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
http://saturn.jpl.nasa.gov/. The Cassini imaging team
homepage is at http://ciclops.org.
