CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Spoke Set

This Cassini view shows a group of more than a dozen spokes in Saturn's outer B ring. The B ring displays the azimuthal asymmetry, or variation with longitude around the planet, that is characteristic of the spoke-forming region.

The large spoke feature above center--most likely a grouping of multiple spokes--is about 5,000 kilometers (3,100 miles) long and 2,000 kilometers (1,200 miles) wide.

Left of center, two dark gaps mark the Cassini Division (4,800 kilometers, or 2,980 miles wide).

This view looks toward the unilluminated side of the rings from about 9 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 28, 2007 at a distance of approximately 1.6 million kilometers (1 million miles) from Saturn. 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 Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. 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-Huygens mission, visit and the Cassini imaging team home page,

Credit: NASA/JPL/Space Science Institute
Released: June 5, 2007 (PIA 08955)
Image/Caption Information
  Spoke Set
PIA 08955

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Alliance Member Comments
colin (CICLOPS) (Nov 27, 2007 at 9:50 AM):

The actual mechanism for spoke formation is still unknown, though there are a few ideas floating around (electron beams from thunderstorms, plasmas formed due to meteor impact, etc). These all involve the levitation of small ice grains off the main ring material since we know that they are made of small charged particles from the way they scatter light and orbit the planet. We have an ongoing campaign to spot spokes actually forming which will tell us a lot more about them if successful. With luck, we'll be able to tell which model is right in the near future.

preston (CICLOPS) (Nov 27, 2007 at 9:49 AM):
Alan - The phase angle here is fairly low. The Sun is behind Cassini and off to the side a bit. -Preston
gandalf (Nov 25, 2007 at 10:30 AM):
Are these spokes caused by magnetic effects...or are we still not completely sure yet ?
alwolfe (Nov 24, 2007 at 3:31 PM):
I'm interested in knowing the sun-ring-camera viewing geometry here...

Kevin S. Moore (Jun 5, 2007 at 11:50 PM):
Here is where the real science is going on.. ! WOW! What are they? The Spokes?
Where do they come from? Can you believe your own eyes? Have I see this before
on earth? Like on a LP record .. spinning.. wonders of wonders. Those spokes
are moving are they not? Vibrating like a guitar strings. 12 strings.. awsome!

a 2nd shifter