CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Edge Wave Shadows

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, 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 PIA11655 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 PIA11651 and PIA11660.

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 Equinox Mission is a joint United States and European endeavor. 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 was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini Equinox Mission visit, and

Credit: NASA/JPL/Space Science Institute
Released: September 14, 2009 (PIA 11579)
Image/Caption Information
  Edge Wave Shadows
PIA 11579

Avg Rating: 9.21/10

Full Size 1020x1020:
PNG 285 KB

Alliance Member Comments
stowaway (Sep 17, 2009 at 0:33 AM):
Sorry... dumb question... Encke Gap... Pan... edge waves... duh
stowaway (Sep 14, 2009 at 10:31 AM):
Along the outside edge of the Encke gap (above Daphnis in the image) there appear to be smaller vertical features casting shadows similarly. Is there an explanation for this?