The strange appearence of the F-Ring

Caption NASA:"The striated appearance of the F-Ring is immediately apparent in the region of the ring that trails behind the moon Prometheus. The F-Ring is characterized here by dark gores that stretch inward toward the planet and forward in the direction of motion.
This image has been expanded in the horizontal direction by a factor of 5 in order to make radial variations more prominent.
The curvature of the Rings is also exaggerated by the horizontal stretch.
The exterior flanking ringlets (to the right of the bright ring core) are not disturbed by Prometheus to the great degree seen in the inner ringlets. This view looks toward the unlit side of the Rings from about 31° above the Ring-Plane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 25, 2006 at a distance of approx. 1,7 MKM (about 1,1 MMs) from Saturn and at a phase angle of 162°. Scale in the original image is roughly 10 km per pixel".