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Cassini-Huygens passing through the gap in the rings

Although the ring gaps appeared empty, they were not. Millions of dust particles were waiting for Cassini-Huygens, and the spacecraft ploughed through them at a relative speed of about 20 kilometres a second. That's about 70 000 kilometres per hour!

The Radio and Plasma Wave Science (RPWS) instrument on Cassini-Huygens measured little puffs of plasma produced by dust impacts. While crossing the plane of Saturn's rings, the instrument detected up to 680 dust hits per second, or roughly 100 000 hits in less than five minutes.

Scientists at University of Iowa, where the RPWS was designed, converted these impacts into audible sounds that resemble hail hitting a tin roof.  
 
Fortunately the particles were small, comparable in size to particles in cigarette smoke, and most of the hits were confined to the spacecraft's high-gain antenna which was turned to face the direction of travel, like an umbrella.
 
 
No damage was done, and the spacecraft reported no unusual activity due to the hits, successfully going into orbit around Saturn on 1 July, but the sounds produced are exciting! You can listen to the sound of passing through the ring dust by clicking here. Listen

The Cassini-Huygens mission is a co-operative project of NASA, ESA and ASI, the Italian space agency.