* Astronomy

Recent computer simulations show Saturn's rings may be more massive and much older than astronomers thought.
   Although Saturn's rings are so thin they disappear when turned edge-on to our line of sight, they apparently contain more material than meets the eye.

"We'll need to rewrite the textbooks on how much mass is in the rings" - Glen Stewart, University of Colorado planetary scientist.

Stewart presented his team's findings Monday at the annual meeting of the American Astronomical Society's Division for Planetary Sciences in Orlando, Florida.

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This image of Saturns rings was taken by the Cassini spaceprobe on October 01, 2007, when it was approximately 573,636 kilometres away.


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Credit NASA/JPL/Space Science Institute

The image was taken using the CL1 and CL2 filters.

3D movie of Saturns rings during a ring plane crossing


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Credit: Scott Sandford, Astrophysics Branch, NASA-Ames Research Centre

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Images taken by Cassinis Magnetospheric Imaging Instrument (MIMI) show that Saturns ring current is a warped disc that balloons out of the equatorial plane on the planets dayside and remains a thin disk that rises above the plane at larger distances on the nightside.

Ring currents surround planets sort of like the brim of a hat. Uniquely in Saturns case, that brim has been crushed at the front and tipped up at the back, so its pretty bent out of shape! - Dr Stamatios Tom Krimigis, the Principal Investigator for the instrument, who is presenting images at the European Planetary Science Congress in Potsdam on Thursday 23rd August.

The presence of a ring current around Saturn was first suggested in the early 1980s following magnetic anomalies observed by the Pioneer 11 and Voyager 1 and 2 spacecraft. Ring currents are also found around Earth and Jupiter. They are caused when plasma becomes trapped between mirror points on magnetic field lines, similar to the Van Allen radiation belts surrounding Earth, and gradually drifts around the planet. The aggregate motion of all of the hot ions distributed around the equator generates an electric current. On Saturn, the source of the plasma is material from the rings and gas vented by geysers on the moon Enceladus, which is subsequently ionised and accelerated. The MIMI images show that the ring current occupies a region of the equatorial plane between 540 000 kilometres and 1 080 000 kilometres from the centre of Saturn. They also show that Saturns ring current is persistently asymmetric (unlike Earths), and that the asymmetry rotates nearly rigidly with Saturn.

MIMI, which was developed by an international team led by the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland, has three distinct sensors that allow it to visualize the invisible and show the plasma and radiation belts in Saturns environment in an image. The MIMI instrument includes an Ion and Neutral Camera developed by APL, a spectrometer built by the University of Maryland, and a low energy particle detector developed by the Max-Planck-Institut fuer Sonnensystemforschung and a number of co-investigator institutions including CESR in Toulouse.

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