Saturn's F ring
With several stars visible in the background, Cassini looks toward Saturn's F ring, where we can see the whispy white tail. The F ring has a unique spiral structure containing very little mass.
The spiral appears to originate from material somehow episodically ejected from the core of the F ring itself, and then sheared out due to the different orbital speeds followed by the surrounding constituent particles.
June 25, 2009 5:00 AM PDT
Photo by: NASA/JPL/Space Science Institute
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