Animated Cassini spacecraft image of towers casting shadows along the edge of Saturn's B ring. The towering structures reach as high as 2.5 kilometres, and are thought to be caused by large bodies, or moonlets, passing by the ring's edge. The rings consist of particles of nearly pure water ice, but they have become contaminated with meteoritic dust over time. At top is part of the Cassini Division, which separates the B and A rings. Image obtained by the spacecraft's narrow-angle camera on the 26th July 2009, at a distance of approximately 336,000 kilometres from Saturn.