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Giant moon collision 'may have formed Saturn's rings'

Saturn's rings may have formed when a large moon with an icy mantle and rocky core spiralled into the nascent planet.

A US scientist has suggested that the tidal forces ripped off some of the moon's mantle before the actual impact.

The theory could shed light on the rings' mainly water-ice composition that has puzzled researchers for decades.

The scientist announced her idea at a conference in Pasadena, US.

Though the rings are now thought to consist of 90-95% water-ice, Robin Canup of the Southwest Research Institute in Boulder said the slight rock content is due to the interplanetary dust and constant "bombardment … by micrometeoroids".

"[The rings] must have formed as essentially pure ice," she said at a meeting of the American Astronomical Society's Division for Planetary Science.

Just how these icy rings came about has always been a mystery.

"You would've expected that if an object, let's say an asteroid or even a satellite had broken up, there would be a large rock component," Carl Murray from Queen Mary, University of London, one the astronomers on the Cassini mission, told BBC News....
Read entire article at BBC News