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Published online 7 October 2009 | Nature | doi:10.1038/news.2009.979
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Huge 'ghost' ring discovered around Saturn
Spitzer Space Telescope reveals a supersized dust belt.
Saturn's ring system has just got a lot larger, with the discovery of a faint ring that stretches out millions of kilometres into space.
But this new ring, which follows the orbit of one of Saturn's moons, Phoebe, is unlike any of the other rings that are closer to the planet: as well as being much thicker and wider, it is tilted from the plane of the other rings.
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The origin of the dark material forming Cassini Regio on Iapetus has long been linked to Phoebe, because of some spectral similarities between material on the surfaces of the two moons. Early ideas proposed some form of micrometeroid sputtering of material from Phoebe, which then spirals in to strike Iapetus (and Hyperion). This new discovery of a ring close to Phoebe adds an interesting twist. It suggests the new material may not have come directly from Phoebe, but instead may be the result of a primordial event involving the destruction of a dark Chiron-like object – with (an)other such event(s) wrecking Hyperion and coating Iapetus.