Saturn Hailstorm: "Saturn Hailstorm

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!

"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.
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