NASA's Cassini spacecraft has captured these images of clumps seemingly embedded within Saturn's narrow outermost F ring. Cassini, which is due to arrive at the ringed planet on July 1, snapped the photos on Feb. 23, 2004, from a distance of 62.9 million kilometers (39 million miles).

Two clumps in particular, one of them extended, can be seen in the upper part of the F ring in the image on the left, and in the lower part of the ring in the image on the right. Other knot-like irregularities in the ring's brightness can also be seen in the right hand image. The small dot at center right in the second image is one of Saturn's small moons, Janus.

Clumps such as these were first seen when the two Voyager spacecraft flew past Saturn in 1980 and 1981. It is not certain what causes these features, though several theories have been proposed, including meteoroid bombardment and inter-particle collisions in the F ring. Contrast has been greatly enhanced, and the images have been magnified, to aid visibility of the F Ring and the clump features.
Image Credit: NASA/JPL/Space Science Institute