PIA11634: Shadow and Spokes


Shadow and Spokes

Caption:

A moon's shadow strikes Saturn's rings near bright spokes on the B ring near the center of this Cassini image taken about one month after the planet's August 2009 equinox.

Mimas, the moon casting the shadow, is not shown. To learn more about the ghostly radial markings called spokes, see PIA11144 and PIA08288 . Spokes appear bright when they are viewed at phase, or Sun-Saturn spacecraft, angles higher than about 45 degrees. The phase angle in this image is 106 degrees.

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 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 8 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 9, 2009. The view was obtained at a distance of approximately 2.9 million kilometers (1.8 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 106 degrees. Image scale is 17 kilometers (11 miles) per pixel.

Background Info:

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 .

Cataloging Keywords:

Name Value Additional Values
Target Saturn Rings B Ring, Mimas, Saturn
System Saturn
Target Type Ring Planet, Satellite
Mission Cassini-Huygens
Instrument Host Cassini Orbiter
Host Type Orbiter
Instrument Imaging Science Subsystem (ISS)
Detector Narrow Angle Camera
Extra Keywords Grayscale, Shadow, Visual
Acquisition Date
Release Date 2009-11-30
Date in Caption
Image Credit NASA/JPL/Space Science Institute
Source photojournal.jpl.nasa.gov/catalog/PIA11634
Identifier PIA11634