Saturn's Rings as Ancient as Solar System

"We have discovered that the rings were probably not created just yesterday in cosmic time, and in this scenario it is not just luck that we are seeing planetary rings now. They probably were always around but continually changing, and they will be around for many billions of years."

Larry Esposito -University of Colorado, Laboratory for Atmospheric and Space Physics

The scientific world is a continuing maelstrom of ideas, being reformed, redefined and refuted. Nothing stays put for long, and this is even more the case in the scientific realm of astronomy. New observations by NASA’s Cassini spacecraft are helping to continue this bafflement of the scientific terra firma, dispelling beliefs that the rings orbiting Saturn are relatively new.

Once thought to have formed during the age of the dinosaurs, nearly 100 million years ago as a result of a disintegrating moon, the Saturn rings may have been created roughly 4.5 billion years ago when the solar system was still under construction.

Larry Esposito, principal investigator for Cassini's Ultraviolet Imaging Spectrograph at the University of Colorado, Boulder, Laboratory for Atmospheric and Space Physics, said data from NASA's Voyager spacecraft in the 1970s and later NASA's Hubble Space Telescope had led scientists to believe Saturn's rings were relatively youthful and likely created by a comet that shattered a large moon some 100 million years ago.

But ring features seen by instruments on Cassini -- which arrived at Saturn in 2004 -- indicate the rings were not formed by a single cataclysmic event, he said. The ages of the different rings appear to vary significantly and the ring material is continually being recycled, Esposito said.

"The evidence is consistent with the picture that Saturn has had rings all through its history," said Esposito. "We see extensive, rapid recycling of ring material, in which moons are continually shattered into ring particles, which then gather together and re-form moons."

Scientists had previously believed rings as old as Saturn itself should be darker due to ongoing pollution by the "infall" of meteoric dust, leaving telltale spectral signatures, Esposito said. But the new Cassini observations indicate the churning mass of ice and rock within Saturn's gigantic ring system is likely much larger than previously estimated, helping to explain why the rings appear relatively bright to ground-based telescopes and spacecraft.

"The more mass there is in the rings, the more raw material there is for recycling, which essentially spreads this cosmic pollution around," said Esposito. "If this pollution is being shared by a much larger volume of ring material, it becomes diluted and helps explain why the rings appear brighter and more pristine than we would have expected."

Esposito, who discovered Saturn's faint F ring in 1979 using data from NASA's Pioneer 11 spacecraft, said an upcoming paper by him and colleagues in the journal Icarus supports the theory that Saturn's ring material is being continually recycled. Observing the flickering of starlight passing through the rings in a process known as stellar occultation, the researchers discovered 13 objects in the F ring ranging in size from 30 yards to six miles across.

Esposito stressed that in the future Saturn's rings won't be the same we see today, likening them to great cities around the world like San Francisco, Berlin or Beijing. "While the cities themselves will go on for centuries or millennia, the faces of people on the streets will always be changing due to continual birth and aging of new citizens."

For more information about the NASA Cassini-Huygens mission visit the Web at saturn.jpl.nasa.gov. To listen to a podcast of Esposito and view a short video animation of objects in Saturn's F ring shattering and re-forming, visit the Web at www.colorado.edu/news/reports/space/.

Posted by Josh Hill.

Link:

http://www.colorado.edu/news/releases/2007/484.html
http://www.physorg.com/news116739036.html