Propeller-shaped structures in Saturn's A ring, which may yield insights into how planets form from disks around stars, have now been tracked for several years. (News release can be found here.)

		Jul 8, 2010:	Propeller Churns the A Ring - This movie created from images obtained by NASA's Cassini spacecraft shows a propeller-shaped structure created by a hidden, embedded moon moving through one of Saturn's rings.
		Jul 8, 2010:	Tracking a Propeller - NASA's Cassini spacecraft captured a propeller-shaped disturbance in one of Saturn's rings created by a moon that is too small to be seen here.
		Jul 8, 2010:	Sunlit Propeller - A propeller-shaped structure created by an unseen moon is brightly illuminated on the sunlit side of Saturn's rings in this image obtained by NASA's Cassini spacecraft.
		Jul 8, 2010:	Propeller from Unlit Side - A propeller-shaped structure created by an unseen moon appears dark in this image obtained by NASA's Cassini spacecraft of the unilluminated side of Saturn's rings.

		Sep 21, 2009:	Giant Propeller in A Ring - An unusually large propeller feature is detected just beyond the Encke Gap in this Cassini image of Saturn's outer A ring taken a couple days after the planet's August 2009 equinox.