Complex Edge Waves
September 2, 2009
Waves in the edges of the Keeler gap in Saturn's A ring, created by the embedded moon Daphnis, show considerable complexity in this image taken as Saturn approached its August 2009 equinox.
Daphnis (8 kilometers, or 5 miles across) orbits in the A ring's Keeler Gap. Equinox has exposed shadows cast by edge waves, or vertical structures of ring material created by Daphnis' gravity (see Wave Shadows in Motion). The low sun illumination angle, and the resulting shadows, have revealed a complexity in these features not seen before.
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 24 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 11, 2009. The view was acquired at a distance of approximately 496,000 kilometers (308,000 miles) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 27 degrees. Image scale is 3 kilometers (2 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