[meteorite-list] Scientists Show Off Specks of Comet Dust (Stardust)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed Feb 1 14:08:11 2006
Message-ID: <200602011906.k11J6Xo24864_at_zagami.jpl.nasa.gov>


Scientists show off specks of planet dust
By Glennda Chui
San Jose Mercury News
January 31, 2006

Scientists at Lawrence Livermore National Laboratory showed off specks
of cosmic treasure Tuesday -- comet dust gathered by NASA's Stardust
mission during a seven-year ramble through space.

"It's very, very exciting," said Hope Ishii, a postdoctoral researcher
at the lab who hand-carried the comet samples back from NASA's Johnson
Space Center Friday on a commercial flight.

"This is cosmic dirt, basically," she said. "It's been frozen since
the planetary system was forming. It really truly is a time capsule for

Samples of the dust -- the ancient stuff out of which our solar system
was built -- are being sent to nearly two dozen laboratories around the
world for quick analysis over the next six months.

They include NASA/Ames Research Center in Mountain View, Stanford
University, the Stanford Linear Accelerator Center, Lawrence Berkeley
National Laboratory and the University of California-Berkeley.

Researchers will be probing the dust with tools that weren't even
invented when the mission was launched seven years ago toward a
rendezvous with Comet Wild 2 (pronounced VILT 2). The sample return
capsule landed in the Utah desert after a fiery re-entry Jan. 15.

At Livermore, physicist Zurong Dai used one of those tools -- the
world's most powerful electron microscope -- to zoom in on a thin slice
of a single dust particle.

Magnified 100,000 times, it looked like a battered gray rock, full of
holes, pits and bumps. Magnified 800,000 times it was grainy, like a
piece of tweed cloth, and speckled with round, dark spots.

At 1.75 million magnification -- the instrument's full power -- orderly
rows of atoms filled the screen.

This particular microscope technology is widely used to examine
materials for the semiconductor industry, said John Bradley, director of
the lab's Institute of Geophysics and Planetary Physics, who is leading
the analysis there. As part of the Stardust mission, NASA funded work at
Livermore to make it even more powerful.

The instrument is so sensitive, Dai said, that "when I take a picture I
have to hold my breath" to keep the image from blurring.

Ishii focused an optical microscope on a tiny cube of "aerogel." The
lightest solid known -- it looks like frozen smoke -- it was used to
trap and protect the dust particles on their way back to Earth. Now
scientists have to figure out how to get the dust out.

The block contained a fish-shaped hole, blasted into the aerogel by a
comet particle coming in at 13,000 mph, Ishii said. The impact split it
in two, and the pieces are still trapped in the aerogel.

Ishii developed a tiny knife with a diamond blade that vibrates at high
frequency and cuts through the brittle aerogel as if it were butter.

"This is the coolest thing I've ever been involved with," she said.
"This is the opportunity of a lifetime."

Other instruments are like salami slicers, chopping individual particles
-- each perhaps one-tenth to one-hundredth the diameter of a human hair
-- into thin sheets for analysis.

The comet dust dates back to the formation of the solar system 4.6
billion years ago, Bradley said. The spacecraft also collected
interstellar dust particles, born in distant stars, that could be
billions of years older.

Put together, all the millions of dust particles would weigh less than a
grain of salt and not quite fill a thimble. But that's enough to keep
scientists busy for decades. And some samples will be kept at Johnson
Space Center, in a building that also houses moon rocks and meteorites,
waiting for even more powerful analytic techniques that have not been
invented yet.

"This is the stuff all the atoms in the solar system came from,"
including those in our bodies, Bradley said. "So in a very real sense,
we're looking at our very earliest atomic and molecular ancestors."
Received on Wed 01 Feb 2006 02:06:32 PM PST

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