Moon, Shadow and Rings
January 1, 2010
Saturn's moon Epimetheus casts a shadow across colorful rings in this image taken before the planet's August 2009 equinox.
Epimetheus (113 kilometers, or 70 miles across) is visible as a small dot at the center of the bottom of the image.
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).
Images taken using red, green and blue spectral filters were combined to create this natural color view. This view looks toward the southern, sunlit side of the rings from about 39 degrees below the ringplane.
The images were obtained with the Cassini spacecraft wide-angle camera on June 8, 2009 at a distance of approximately 725,000 kilometers (450,000 miles) from Saturn. Image scale is 40 kilometers (25 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