October 22, 2009
Moon shadows are cast on Saturn's A ring in this image taken almost a month after the planet's August 2009 equinox.
Pan (28 kilometers, or 17 miles across) orbits in the Encke Gap of the A ring and can be seen casting a narrow shadow on the right side of the image. Daphnis (8 kilometers, or 5 miles across) orbits in the Keeler Gap of the A ring and, although the moon itself is not discernible, the shadows cast by the moon's attendant edge waves are visible to the left in the image. To learn more about Daphnis' edge waves, see Rippling Shadows.
Bright specks in the image are 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 Across Resplendent Rings), but also the shadows of newly revealed vertical structures in the rings themselves (see A Small Find Near Equinox).
This view looks toward the northern, sunlit side of the rings from about 9 degrees above the ringplane.
Scale in the original image was 17 kilometers (11 miles) per pixel. The image has been magnified by a factor of two and contrast-enhanced to aid visibility. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 7, 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 102 degrees.
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