"Propeller" features were first spotted in close-up images of the ring taken by Cassini during its orbit insertion. Scientists determined that they indicate the presence of isolated 100-meter-size objects within the rings -- bodies intermediate in size between things that are named as moons and the innumerable individual particles that make up the rings themselves. This propeller, spotted just after equinox on August 13, 2009, is very bright because it sticks up above the ring plane at a time when the

NASA / JPL / SSI