Hail through Saturn's ring plane

The Cassini spacecraft just tweeted about what it sounded like when it arrived at Saturn and passed through the ring plane in 2004. While the spacecraft did not fly through the visible rings, there seems to be enough dust forming an invisible ring where it passed through to pelt the spacecraft with a lot of dust. These must have been truly microscopic dust, since if they were big enough to be visible enough to be seen by the naked eye, they would probably have destroyed the spacecraft at the speeds it was traveling.