Edge Wave Shadows
September 14, 2009
Vertical ring structures created by the moon Daphnis cast dark shadows on Saturn's A ring in this image taken as the planet approached its August 2009 equinox.
Daphnis (8 kilometers, or 5 miles across) is a bright dot casting a thin shadow just in the middle right side of the image. The moon has an inclined orbit, and its gravitational pull perturbs the orbits of the particles of the A ring forming the Keeler Gap's edges and sculpts the edges into waves having both horizontal (radial) and out-of-plane components. See Wave Shadows in Motion to learn more and to see a movie of this process.
The novel illumination geometry created around the time of Saturn's August 2009 equinox allows out-of-plane structures and 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 movies of moons' shadows moving across the rings, see Moon Shadow in Motion and Weaving a Shadow.
This view looks toward the unilluminated side of the rings from about 38 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 15, 2009. The view was obtained at a distance of approximately 1.7 million kilometers (1.1 million miles) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 92 degrees. Image scale is 10 kilometers (6 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