Saturn's moon Prometheus casts a shadow near a streamer-channel created by
the moon in the thin F ring in this image taken about a month after the
planet's August 2009 equinox.
Pandora (81 kilometers, or 50 miles across) can also be seen on the right
of the image. Pandora orbits outside the F ring and, with the inner
shepherd moon Prometheus, helps to keep the narrow lanes of the F ring in
check. The gravity of potato-shaped Prometheus (86 kilometers, or 53 miles
across) periodically creates streamer-channels in the F ring, and the
moon's handiwork can be seen below the shadow in this image. To learn more
and to watch a movie of this process, see PIA08397.
The shadow of the planet cuts across the bottom of the image.
Bright specks in the image are background stars.
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 sunlit, northern side of the rings from about 6
degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft
narrow-angle camera on Sept. 13, 2009. The view was obtained at a distance
of approximately 2.6 million kilometers (1.6 million miles) from Saturn
and at a Sun-Saturn-spacecraft, or phase, angle of 117 degrees. Image
scale is 15 kilometers (9 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
http://saturn.jpl.nasa.gov/. The Cassini imaging team
homepage is at http://ciclops.org.