The partial shadow of the moon Tethys demonstrates the variations in density across Saturn's rings.
As the Cassini spacecraft looks toward the unilluminated side of the rings from about 37 degrees above the ring plane, part of Tethys' shadow is seen lying across the A ring and Cassini Division. The densest part of the A ring and the denser B ring let neither sunlight nor the darkness of Tethys' shadow pass through to the spacecraft's camera, so the moon's shadow appears cut off. The B ring instead appears brightly lit here from Saturnshine. Tethys is not shown.
As Saturn approaches its August 2009 equinox, the planet's moons cast shadows onto the rings. To learn more about this special time and to see a movie of a moon's shadow moving across the rings, see PIA11651.
The image was taken in visible light with the Cassini spacecraft wide-angle camera on April 17, 2009. The view was obtained at a distance of approximately 1.3 million kilometers (808,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 120 degrees. Image scale is 75 kilometers (46 miles) per pixel.
The Cassini Equinox Mission is a joint United States and European endeavor. 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 was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.