CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Wavy Shadows

Wavy Shadows
PIA 11656

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Wavy Shadows
PIA 11656

Avg Rating: 8.09/10

Scaled and Cropped 1010x1010:
PNG 274 KB
  Looming vertical structures, seen here for the first time and created by Saturn's moon Daphnis, rise above the planet's otherwise flat, thin disk of rings to cast long shadows in this Cassini image.

Daphnis, 8 kilometers (5 miles) across, occupies an inclined orbit within the 42-kilometer (26-mile) wide Keeler Gap in Saturn's outer A ring. Recent analyses by imaging scientists published in the Astronomical Journal illustrate how the moon's gravitational pull perturbs the orbits of the particles forming the gap's edge and sculpts the edge into waves having both vertical and horizontal components.

Measurements of the shadows in this and other images indicate that the vertical structures range between one-half to 1.5 kilometers tall (about one-third to one mile), making them as much as 150 times as high as the ring is thick. The main A, B and C rings are only about 10 meters (about 30 feet) thick. Daphnis itself can be seen casting a shadow onto the nearby ring.

A second version of the image that has been magnified to six times its original size and cropped is also shown here.

This image of shadows on the rings and others like it (see PIA11653 and PIA11655) are only possible around the time of Saturn's equinox which occurs every half-Saturn-year, equivalent to about 15 Earth years. The illumination geometry that accompanies equinox lowers the sun's angle to the ringplane and causes out-of-plane structures to cast long shadows across the rings.

This view looks toward the unilluminated side of the rings from about 49 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 13, 2009. The view was obtained at a distance of approximately 1.2 million kilometers (746,000 miles) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 56 degrees. Image scale is 7 kilometers (5 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: June 11, 2009 (PIA 11656)
Image/Caption Information

Alliance Member Comments
CheshireCat (Jun 23, 2009 at 9:29 AM):

The "horizontal" component (I prefer "radial") is due to the moon's passage. It happens any time a nearby moon passes a group of particles. It's actually those waves that we used to find Pan and Daphnis since they're diagnostic of the moon's presence. The vertical waves are due to the moon's vertical motion. They only occur for a moon on an inclined orbit.

So there's not really a particularly close connection between the two waves, other than the moon is the cause. You always get the radial, but you don't always get the vertical.

--- John Weiss, CICLOPS
billclawson (Jun 22, 2009 at 2:44 PM):
Absolutely amazing. Is there any explanation as to why both vertical and horizontal displacement is occurring in the waves? If the moon was travelling through air, you could almost call it wing-tip vortexes.
mipsandbips (Jun 11, 2009 at 6:39 PM):
In a word, unparalleled!