Seen from the unlit side of Saturn's A ring, the shadow of the moon Janus is cast across the Encke Gap.
The varying darkness of the shadow is due to varying particle density across the ring. To learn more and to watch a movie of a moon's shadow moving across the unlit side of the rings, see Weaving a Shadow.
The novel illumination geometry created as Saturn approaches its August 2009 equinox allows moons orbiting in or near the plane of Saturn's equatorial rings to cast shadows onto 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. To learn more about this special time and to see a movie of a moon's shadow moving across the rings, see Moon Shadow in Motion.
Janus is not shown in this image.
This view looks toward the unilluminated side of the rings from about 51 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 28, 2009. The view was obtained at a distance of approximately 1.4 million kilometers (870,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 54 degrees. Image scale is 8 kilometers (5 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.
Credit: NASA/JPL/Space Science Institute