Saturn's G-ring
Saturn's g-ring
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Friday, 03, Aug 2007 04:50
Scientists believe they have discovered the cause of Saturn's mysterious G-ring.
First spotted by the spacecraft Voyager, the faint and narrow ring lies beyond the main set of rings – a location which has puzzled astronomers.
It has no moons flanking it - which could 'shepherd' it and carve it out - and it is 15,000km from the nearest satellite and 168,000km from the centre of Saturn.
Writing in the journal Science, an international team of astronomers describe how the Cassini spacecraft provided a new view of the ring and they were able to identify what it is composed of.
They claim it is likely to be produced by relatively large, icy particles that reside within a bright arc on the ring's inner edge and are kept there by gravitational effects from Saturn's moon Mimas.
As micrometeoroids collide with the particles, they release small, dust-sized particles that brighten the arc.
The plasma from Saturn's magnetic field then sweeps through the arc, dragging out the fine particles and creating the G-ring.
"Distant pictures from the cameras tell us where the arc is and how it moves, while plasma and dust measurements taken near the G ring tell us how much material is there," said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca.
Cassini scientists are now looking forward to getting a closer view of the G-ring's source bodies when the spacecraft flies about 600 miles from the arc 18 months from now.