NASA / JPL-Caltech / SSI / animation by Mike Malaska
Spinning spokes in Saturn's rings
Cassini captured this 22-frame animation of the "spokes" in Saturn's rings on 7 September 2009. Scientists think that the spokes are made of fine dust electrostatically levitated above the ring surface, made more visible by the low-angle lighting that occurs near equinox. (It may also be possible that the spoke phenomenon only occurs at this season; scientists don't yet know for sure). The images were aligned and their contrast adjusted to make this animation smooth. A higher-resolution version can be downloaded from Mike Malaska's flickr page.