The outer edge of Saturn's B ring is controlled by an orbital resonance with the satellite Mimas, whose gravitational perturbations there give the ring-edge a scalloped appearance. That ring-edge has been monitored by the Cassini spacecraft that also orbits there, and several movies showing ring's complex movements are now posted at the CICLOPS website. The above image shows a closeup of the B ring's outer edge seen during equinox, when the sunlight was streaming nearly parallel to the ring place. Note the shadows cast by the bright material at the ring's outer edge. It is thought that these shadows are due to one or more small moonlets also hidden somewhere at the ring-edge. If so, then the moonlet's gravitational pull might be responsible for displacing the ring particles perpendicular to the ring plane, causing particles to pile-up into kilometer-tall mountains that cast those very prominent shadows.