[meteorite-list] Saturn's Rings May be Old Timers

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Wed, 19 Dec 2007 19:28:37 -0700 (MST)
Message-ID: <1560.71.226.60.25.1198117717.squirrel_at_timber.lpl.arizona.edu>

Hi All:

This idea is not new. Don Davis et al. published a similar model more than
20 years ago. It is also interesting how similar the artist concept of the
rings in the article is to one done by Bill Hartmann something like 30
years ago. It would be nice if people gave credit where credit was due.

Larry

On Wed, December 19, 2007 2:41 pm, Ron Baalke wrote:
>

> http://www.jpl.nasa.gov/news/news.cfm?release=2007-149
>
>
> Saturn's Rings May be Old Timers
> Jet Propulsion Laboratory
> December 12, 2007
>
>
> SAN FRANCISCO, Calif. - New observations by NASA's Cassini spacecraft
> indicate the rings of Saturn, once thought to have formed during the age of
> the dinosaurs, instead 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, said data from
> NASA's Voyager spacecraft in the 1970s, and later from NASA's Hubble
> Space Telescope, led scientists to believe Saturn's rings were
> relatively youthful and likely created by a comet that shattered a large
> moon, perhaps 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. 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 of the University of Colorado's
> Laboratory for Atmospheric and Space Physics. "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."
>
> Esposito and colleague Miodrag Sremcevic, also with the University of
> Colorado, are presenting these findings today in a news briefing at the
> meeting of the American Geophysical Union in San Francisco.
>
> "We have discovered that the rings probably were not created just
> yesterday in cosmic time, and in this scenario, it is not just luck that we
> are seeing planetary rings now," said Esposito. "They probably were always
> around but continually changing, and they will be around for many billions
> of years."
>
> 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. This
> helps explain why the rings overall 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," he
> said. "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 expected."
>
> Esposito, who discovered Saturn's faint F ring in 1979 using data from
> NASA's Pioneer 11 spacecraft, said a paper by him and his colleagues
> appearing in an upcoming issue of 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 27 meters to 10 kilometers (30 yards to six miles)
> across.
>
> Since most of the objects were translucent -- indicating at least some
> starlight was passing through them -- the researchers concluded they
> probably are temporary clumps of icy boulders that are continually
> collecting and disbanding due to the competing processes of shattering and
> coming together again. The team tagged the clumpy moonlets with cat names
> like "Mittens" and "Fluffy" because they appear to come and go
> unexpectedly over time and have multiple lives, said Esposito.
>
> Esposito stressed that Saturn's rings of the future won't be the same
> rings 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."
>
> The Cassini-Huygens mission is a cooperative project of NASA, the
> European Space Agency and the Italian Space Agency. The Jet Propulsion
> Laboratory, a division of the California Institute of Technology in
> Pasadena, manages the mission for NASA's Science Mission Directorate in
> Washington, D.C.
>
>
> For more information about the Cassini-Huygens mission, visit:
> http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini . 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:
> http://www.colorado.edu/news/reports/space/.
>
>
> ------------------------------------------------------------------------
>
>
> Media Contact: Carolina Martinez 818-354-9382
> Jet Propulsion Laboratory, Pasadena, Calif.
> carolina.martinez at jpl.nasa.gov
>
> Jim Scott 303-492-3114
> University of Colorado, Boulder
> jim.scott at colorado.edu
>
> 2007-149
>
>
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Received on Wed 19 Dec 2007 09:28:37 PM PST