[meteorite-list] NASA Research Finds Green Sand Crystals Are in Comet Tempel 1

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Sep 15 18:30:09 2005
Message-ID: <200509152228.j8FMSwh02813_at_zagami.jpl.nasa.gov>

http://www.nasa.gov/centers/ames/research/exploringtheuniverse/comettemple1.html

John Bluck
NASA Ames Research Center, Moffett Field, Calif.
Phone: 650/604-5026
E-mail: jbluck_at_mail.arc.nasa.gov

NASA Research Finds Green Sand Crystals Are in Comet Tempel 1
September 15, 2005

Green sand found on the big island of Hawaii resembles olivine crystals
in the icy interior of comet Tempel 1, according to a NASA astrophysicist.

Scientists revealed that they detected green silicate crystals (olivine)
in Tempel 1 similar to, but smaller than, Hawaiian green sand particles,
according to articles by the researchers in the September 15, 2005 issue
of the journal Science Express. They made their observations before,
during and after the NASA Deep Impact spacecraft's 820-pound 'impactor'
collided with the comet in early July 2005, as planned, so astronomers
could determine what is in comets. The papers outline findings
scientists made using infrared detectors on the Gemini and Subaru
telescopes in Hawaii.

"The silicate crystals are talcum powder-size, but they are made of the
same materials as the green sand beaches in Hawaii," said Diane Wooden,
a co-author of both papers. She is an astrophysicist at NASA Ames
Research Center, located in California's Silicon Valley. The principal
author of the Gemini Telescope paper is David Harker, University of
California, San Diego. Seiji Sugita of the University of Tokyo is the
principal author of the second Subaru Telescope paper.

"Following the collision of the comet with the 'impactor,' there was a
short-lived gas geyser associated with the impact site that carried the
crystals from Tempel 1 into space," Wooden said. "The Gemini and the
Subaru telescopes are two of the biggest in the world, and we were able
to focus in on the green dust particles in the jet and ejecta ???
something that most space-borne telescopes could not see in infrared
light," she noted.

"The insides of comet Tempel 1 look very much like the outsides of
comets that have not been 'cooked' by passages close to the sun," Wooden
said. She explained that there might be green silicates on the surfaces
of comets that swarm in the outer reaches of the solar system and are
not exposed to intense sunshine.

Another comet, Hale-Bopp, was so active that it released green silicate
crystals as it passed close to the sun in 1997, according to Wooden.

"However, the Deep Impact spacecraft's 'impactor' had to blast the green
silicate crystals from the interior of the comet Tempel 1 for us to see
them with our ground-based instruments," she noted.

Tempel 1 travels close to the sun during part of the comet's orbit, and
strong sunlight hits the comet, causing its surface gases and other
particles to fly off into space. These particles are what make up a
comet's tail, which forms nearer the sun. "In Tempel 1's case, it has
passed near the sun so many times that it has lost much of its surface
gases and particles," said Wooden.

"What's incredible to me is that the surface -- or maybe the fluffiness
of the body of Tempel 1 -- is protecting the primitive particles and
gases just below the surface from being out-gassed," ventured Wooden.

"We discovered crystalline silicates in the dust that flew from the
comet after its collision with the Deep Impact 'impactor.' We don't
usually see these silicates in comets that have been 'cooked' by the
sun," Wooden explained.

Digital images of olivine particles from a green sand beach in Hawaii
and other images related to this story can be found at:

http://www.nasa.gov/centers/ames/multimedia/images/2005/olivine.html

A movie is available on-line that shows the collision of the comet with
Deep Impact's projectile:

http://www.nasa.gov/mov/121527main_MRI_impact.mov
Received on Thu 15 Sep 2005 06:28:58 PM PDT