A natural-color mosaic of Cassini narrow-angle camera images of the unilluminated side of Saturn's D, C, B, A and F rings (left to right) taken on May 9, 2007. The rings are lettered in order of discovery. The A and B rings, separated by the Cassini Division, are the densest; together with the C ring, they constitute the planet's main rings. The D ring is classified as a dusty ring, like the E and G rings (not pictured here), because of the tiny size of its particles. The F ring is a dynamic mixture of larger and smaller particles.Photograph: NASA/JPL/Space Science Institute