Thursday, March 31, 2011

Forensic Sleuthing Ties Ring Ripples to Impacts-NASA's Information

scientists working with data from NASA's Cassini, Galileo and New Horizons missions have traced telltale ripples in the rings of Saturn and Jupiter back to collisions with cometary fragments dating back more than 10 years ago. The ripple-producing culprit, in the case of Jupiter, was comet Shoemaker-Levy 9, whose debris cloud hurtled through the thin Jupiter ring system during a kamikaze course into the planet in July 1994. Scientists attribute Saturn's ripples to a similar object – likely another cloud of comet debris -- plunging through the inner rings in the second half of 1983. The findings are detailed in a pair of papers published online today in the journal Science.

"What's cool is we're finding evidence that a planet's rings can be affected by specific, traceable events that happened in the last 30 years, rather than a hundred million years ago," said Matthew Hedman, a Cassini imaging team associate, lead author of one of the papers, and a research associate at Cornell University, Ithaca, N.Y. "The solar system is a much more dynamic place than we gave it credit for." From Galileo's visit to Jupiter, scientists have known since the late 1990s about patchy patterns in the Jovian ring. But the Galileo images were a little fuzzy, and scientists didn't understand why such patterns would occur. The trail was cold until Cassini entered orbit around Saturn in 2004 and started sending back thousands of images. A 2007 paper by Hedman and colleagues first noted corrugations in Saturn's innermost ring, dubbed the D ring.

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