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Saturn Hailstorm:: Go here and listen to the quitcktime file of the sound generated from the following:

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!

"When we crossed the ring plane, we had roughly 100,000 total dust hits in less than five minutes," says Cassini science team member Don Gurnett of the University of Iowa. Fortunately the particles were small--"comparable in size to particles in cigarette smoke," he says. And most of the hits were to the spacecraft's tough high-gain antenna.

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.