[meteorite-list] Aerogel Helps Scientists Unravel Mysteries of Comets

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Jan 12 21:24:53 2006
Message-ID: <200601130223.k0D2NE809630_at_zagami.jpl.nasa.gov>

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

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

Aerogel Helps Scientists Unravel Mysteries of Comets
January 10, 2006

Strange stuff called 'aerogel' that looks like a semi-transparent, blue
cloud, but that is solid, is carrying captured comet dust to Earth for a
Jan. 15, 2006, landing in a Utah desert.

In January 2004, the Stardust spacecraft flew within 147 miles (236
kilometers) of the comet Wild 2 (VILT-TWO) and survived the high-speed
impact of millions of dust particles and small rocks up to nearly
two-tenths of an inch (one-half centimeter) across. With its
tennis-racket-shaped collector extended, Stardust captured thousands of
comet particles in the see-through aerogel, which includes silica and
oxygen.

"It's a little bit like collecting BBs by shooting them into Styrofoam,"
said Scott Sandford, an astrophysicist and Stardust mission
co-investigator based at NASA Ames Research Center in California's
Silicon Valley. "Some of the grains are likely to have exotic isotopic
ratios that will give us an indication that we're looking at materials
that aren't as old as the solar system, but that are, in fact, older
than the solar system," Sandford asserted.

Another mission objective was to expose the spacecraft to the
interstellar dust stream for 150 days to grab particles. After
collecting them, the aerogel collector retracted into the spacecraft's
capsule. Stardust will be the first mission to capture and return a
substantial sample from outside Earth's moon system.

Making sure that precious comet and interstellar particles imbedded in
the aerogel are not affected by earthly contaminants was an important
task to complete before the Stardust spacecraft was launched on Feb. 7,
1999, from Cape Canaveral Air Station, Florida. aboard a Delta II rocket.

"Under Dr. Sandford's guidance, I performed the lab analysis of the
aerogel using infrared (IR) light to determine the level of organic
contamination," said Max Bernstein, a scientist at NASA
Ames. "These and other preliminary lab tests ultimately led the Stardust
aerogel development team to devise a bake-vacuum-bake cycle to reduce
the carbon content in aerogel," Bernstein said.

"Aerogel is made mostly of sand (silica), and what we're interested in
is the organic material in the cometary samples," Bernstein said. "We
measured organic contamination in aerogel early on. We raised a concern,
and Peter Tsou and the aerogel team at the Jet Propulsion Laboratory in
Pasadena, Calif., devised a method to reduce carbon content in aerogel
by a factor of 10."

Infrared light that astronomers use to detect organic molecules in space
also can be used to measure organic molecules in the laboratory. In
their laboratory, Ames scientists shined IR light though a piece of an
early batch of test aerogel, and they saw organic contamination. Because
infrared is light that is not visible to the human eye, scientists use
special detectors to 'see' IR. If scientists detect a specific IR color
scheme, they can tell that a specific molecular fragment is moving and
is present in the sample of material they are examining.

"If you understand that color scheme, then when you make the
measurement, you can say, 'ah hah, I spotted colors corresponding to a
carbon-hydrogen motion, so there must be carbons and hydrogen in the
aerogel, not just silicon and oxygen,'" Bernstein explained. "Thanks in
part to our measurements, we now have cleaner aerogel, which is flying
on the Stardust spacecraft."

In cooperation with Bernstein, graduate student Maegan K. Spencer of
Stanford University, Stanford, Calif., is conducting more sophisticated
aerogel organic contamination tests in the laboratories of Stanford
Professor Richard Zare.

The returning Stardust capsule will strike Earth's atmosphere at eight
miles (12.8 kilometers) per second - more than 20 times faster than a
speeding bullet. That is fast enough to go from San Francisco to Los
Angeles in only one minute. The 101-pound (45.7 kilogram) conical object
will hurtle through the atmosphere and slow before the spacecraft
finally parachutes down to Earth in a Utah dry lake. The landing will
occur on Sunday, Jan. 15, 2006, at about 3 a.m. MST, in a restricted
area - the Utah Test and Training Range, located southwest of Salt Lake
City.

"There will be a team of scientists at Johnson Space Center who will
assess what we actually got back from the comet so we can verify we did
get a useful sample," Sandford said. "A small portion of the samples
will then be used to make a preliminary study of the returned material.
After the preliminary examination is complete, all the samples will be
made available to the general scientific community for more detailed
study. My guess is people will be asking for and working on these
samples for decades to come."
Received on Thu 12 Jan 2006 09:23:14 PM PST