THE mystery of how Saturn's rings were formed may be solved in 2004, when the spacecraft Cassini is due to arrive. There's one problem though: the spacecraft won't be allowed to fly through the denser rings in case it's hit by a large boulder.
Fortunately, researchers in Norway have devised a way of studying the rings without endangering the spacecraft. The idea is to analyse the V-shaped wakes that boulders leave in the rings' "dusty plasma"ionised gases that contain small particles of solid matter.
As the bigger boulders fly through the rings, they leave behind a cone-shaped wake similar to the pattern of shock waves a supersonic jet makes when it breaks the sound barrier. The width and shape of these "Mach cones" will reveal the size of the dust particles, as well as their density and charges.
Once they know how the dusty plasma reacts to disturbance, researchers hope ...
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