[meteorite-list] Saturn is Like an Antiques Shop, Cassini Suggests

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 27 Mar 2013 11:10:18 -0700 (PDT)
Message-ID: <201303271810.r2RIAILq013581_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2013-117

Saturn is Like an Antiques Shop, Cassini Suggests
Jet Propulsion Laboratory
March 26, 2013

A new analysis of data from NASA's Cassini spacecraft suggests that
Saturn's moons and rings are gently worn vintage goods from around the
time of our solar system's birth.

Though they are tinted on the surface from recent "pollution," these
bodies date back more than 4 billion years. They are from around the
time that the planetary bodies in our neighborhood began to form out of
the protoplanetary nebula, the cloud of material still orbiting the sun
after its ignition as a star. The paper, led by Gianrico Filacchione, a
Cassini participating scientist at Italy's National Institute for
Astrophysics, Rome, has just been published online by the Astrophysical
Journal.

"Studying the Saturnian system helps us understand the chemical and
physical evolution of our entire solar system," said Filacchione. "We
know now that understanding this evolution requires not just studying a
single moon or ring, but piecing together the relationships intertwining
these bodies."

Data from Cassini's visual and infrared mapping spectrometer (VIMS) have
revealed how water ice and also colors -- which are the signs of
non-water and organic materials --are distributed throughout the
Saturnian system. The spectrometer's data in the visible part of the
light spectrum show that coloring on the rings and moons generally is
only skin-deep.

Using its infrared range, VIMS also detected abundant water ice - too
much to have been deposited by comets or other recent means. So the
authors deduce that the water ices must have formed around the time of
the birth of the solar system, because Saturn orbits the sun beyond the
so-called "snow line." Out beyond the snow line, in the outer solar
system where Saturn resides, the environment is conducive to preserving
water ice, like a deep freezer. Inside the solar system's "snow line,"
the environment is much closer to the sun's warm glow, and ices and
other volatiles dissipate more easily.

The colored patina on the ring particles and moons roughly corresponds
to their location in the Saturn system. For Saturn's inner ring
particles and moons, water-ice spray from the geyser moon Enceladus has
a whitewashing effect.

Farther out, the scientists found that the surfaces of Saturn's moons
generally were redder the farther they orbited from Saturn. Phoebe, one
of Saturn's outer moons and an object thought to originate in the
far-off Kuiper Belt, seems to be shedding reddish dust that eventually
rouges the surface of nearby moons, such as Hyperion and Iapetus.

A rain of meteoroids from outside the system appears to have turned some
parts of the main ring system - notably the part of the main rings known
as the B ring -- a subtle reddish hue. Scientists think the reddish
color could be oxidized iron -- rust -- or polycyclic aromatic
hydrocarbons, which could be progenitors of more complex organic molecules.

One of the big surprises from this research was the similar reddish
coloring of the potato-shaped moon Prometheus and nearby ring particles.
Other moons in the area were more whitish.

"The similar reddish tint suggests that Prometheus is constructed from
material in Saturn's rings," said co-author Bonnie Buratti, a VIMS team
member based at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"Scientists had been wondering whether ring particles could have stuck
together to form moons -- since the dominant theory was that the rings
basically came from satellites being broken up. The coloring gives us
some solid proof that it can work the other way around, too."

"Observing the rings and moons with Cassini gives us an amazing
bird's-eye view of the intricate processes at work in the Saturn system,
and perhaps in the evolution of planetary systems as well," said Linda
Spilker, Cassini project scientist, based at JPL. "What an object looks
like and how it evolves depends a lot on location, location, location."

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,
Pasadena, manages the mission for NASA's Science Mission Directorate,
Washington, D.C. The visual and infrared mapping spectrometer team is
based at the University of Arizona, Tucson.

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook at jpl.nasa.gov

2013-117
Received on Wed 27 Mar 2013 02:10:18 PM PDT