An instrument onboard Cassini recorded a flurry of tiny particles pelting the spacecraft as it crossed Saturn's dusty ring plane.
July 9, 2004: When the Cassini spacecraft reached Saturn on June 30th, it dashed through a gap in Saturn's rings ... and then did it again. The double ring crossing was part of a maneuver required to put Cassini in orbit.
Although the ring gaps appeared empty, they weren't. Innumerable bits of ring-dust were waiting for Cassini, and they plowed into the spacecraft at a relative speed of approximately 20 km/s. That's 45,000 mph!
No damage was done, but it sounded exciting.
Each time a dust particle hit Cassini, the impact produced a puff of plasma--a tiny cloud of ionized gas. Cassini's Radio and Plasma Wave Science (RPWS) instrument was able to count these clouds; there were as many as 680 puffs per second. "We converted these into audible sounds that resemble hail hitting a tin roof," says Gurnett, the intrument's principal investigator. Click to listen: 2 MB Quicktime file.
The spacecraft reported no unusual activity due to the hits and performed flawlessly, successfully going into orbit around Saturn--a thrilling start to Cassini's four-year mission of exploration. More thrills are coming: visit the Cassini home page for updates.