August 5, 2009
Atlas joins other moons casting shadows on Saturn's rings as the planet approaches its August 2009 equinox.
Atlas (30 kilometers, or 19 miles across) orbits in the Roche Division between the A ring and the thin F ring, and the moon can be see here casting its shadow on the A ring and across the narrow Keeler Gap. 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 movies of moons' shadows moving across the rings, see Moon Shadow in Motion and Weaving a Shadow.
Stars can be seen through the rings and in the background. They appear elongated because of the camera's long exposure time.
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 June 28, 2009. The view was obtained at a distance of approximately 1.5 million kilometers (932,000 miles) from Atlas and at a Sun-Atlas-spacecraft, or phase, angle of 82 degrees. Image scale is 9 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