Look at this photo of Saturn's rings from earlier this month. Wondering what those little jagged lines are, on top of the thick white band? They're shadows of Saturn ring debris. Click through for larger.
The Planetary Society Blog explains it all:
We're only a few months away from Saturn's equinox, the day when the Sun will pass through the plane of Saturn's rings. So to an observer standing on Saturn's rings, the Sun is beginning to set, and casting long shadows... I believe that what we're actually seeing is clumpiness of particles at the outer edge of the densest B ring, where particles bunch together partially by self-gravity (which would make them more like moons) but also by the periodic gravitational shoves they get from [Saturn's moon] Mimas.
We'll have to wait for higher resolution photos to be sure, but it looks beautiful no matter what it is.
Moon Shadow, Moon Shadow [Planetary Society] (Thanks, Dave)