[meteorite-list] Meteorite Hunting In Antarctica

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:01:34 2004
Message-ID: <200206211805.LAA04639_at_zagami.jpl.nasa.gov>

http://www.thestandard.com.au/IDG2.NSF/cw_AllHeadlines/33B1CD1F0A10AB93CA256BD6007BB800?OpenDocument

Meteorite hunting in Antarctica
BY NADIA CAMERON
The Industry Standard (Australia)
Source : Computerworld
June 13, 2002

It's a haven for scientists studying the Earth's climate and ecological
conditions; it's a rich mineral source and a home to penguins and seals,
but at first glance it's hard to comprehend what Antarctica and outer
space have in common.

For the organisations behind the North American Antarctic Search for Meteorite
(ANSMET) Program however, the answer's simple: it's one of the Earth's best and
most reliable sources of new, non-microscopic extraterrestrial material.

The ANSMET Program is a collaborative effort of US National Science
Foundation's (NSF) Antarctica Program, NASA and the Smithsonian Institution.
The Program's primary aim is to search for, characterise and make available to
researchers worldwide the unbiased and uncontaminated samples of meteorites
recovered from Antarctica.

The NSF says meteorites collected from Antarctica have helped to extend
knowledge of the solar system, revealed the geological nature of asteroids and
have even contributed to unravelling planetary conditions on the moon and Mars.

More than 10,000 meteorite specimens have been recovered in Antarctica since
annual meteorite expeditions began in 1976. According to the NSF, the region
is one of the best places on Earth to search for meteorites for two reasons.
Firstly, while meteorites fall all over the globe they are much easier to spot
if the background material is light-coloured and plain - like ice. Secondly,
there are few terrestrial rocks along the Antarctica plain to complicate the
search.

"Along the margins of the ice sheet, ice flow is sometimes blocked by
mountains and other obstructions, exposing slow-moving or stagnant ice to the
fierce 'katabatic' winds that roar down the ice cap from the South Pole to the
ocean," the NSF says.

"These winds, in turn, scour away the ice, leaving behind a deposit of
meteorites representing those that were sprinkled throughout the volume of ice
lost to the wind. When such a process continues for tens or hundreds of
thousands of years, as is the case in Antarctica, the concentration of
meteorites can be spectacular."

Scott Borg, program director of the NSF's Antarctic Geology and Geophysics
Program, says the meteorite expeditions are undertaken in a "low tech" way,
with the field party crossing the chosen area on snowmobile or on foot.

Six-person recovery teams fly out aboard ski-equipped aircraft from McMurdo
Station, the main US research station in Antarctica, for remote field sites
where they spend a period of five to seven weeks. From the landing site, the
field team moves to a meteorite-stranding surface where systematic searching
begins. To search, the field team members form a line roughly 30 metres apart
and slowly drive across the icefield.

When a sample is located on the surface, it is assigned an identification
number and is given a position using Global Positioning System (GPS)
technology. The field party will also take initial notes about its possible
classification and any distinguishing features such as the fragment's shape
and colour. The fragment is then bagged in a sterile Teflon bag and kept
frozen until it reaches the Antarctic Meteorite Curation Facility at NASA's
Johnson Space Centre (JSC) in Houston, Texas, where it is then analysed or
sent on to another research facility.

Although he believes there is no efficient substitute for the human brain and
eye, Borg says the use of GPS technology on these meteorite expeditions can
be beneficial to researchers for a variety of reasons.

"For strictly meteorite research purposes, GPS locations in tens of metres
are important in determining which fragments should be paired together, for
instance, did they come from the same body that fell from space," he said.

"Often, several fragments are found even though they came from the same body,
and sometimes those fragments are found in different seasons. Hence low-level
GPS positioning is really useful to determine the location on otherwise pretty
featureless ice surfaces."

Another way GPS is important is in understanding how the blue ice stranding
surfaces work, Borg said. Blue ice is a term used for significant areas of ice
that look light blue in colour. The colour is a result of the scattering of
light in the ice.

Blue ice areas are found where the atmospheric conditions such as high wind and
low humidity, preclude snow accumulation and cause the ice sheet to ablate
(erode away via sublimation and wind abrasion). During this process, glacial
ice, which originated as snow but got compacted into ice over time, is exposed.

In particular, GPS can help researchers understand how much blue ice ablates
each year, Borg said.

"We know that surfaces can ablate 10cm or more, so if you can quantify this you
can estimate the rate of flow into the region and address glaciological and
climatological questions," he said.

In order to do this, researchers would place stakes in the surface sufficiently
deep to be able to get several measurements for ablation rate calculations. For
meteorites, researchers could use this type of information to estimate when
field parties should go back to search again by estimating when new meteorites
will surface as the ice ablates. In turn, this information could be used to
estimate the concentration of meteorites in volumes of ice, he said.

- Dr Ralph Harvey of Case Western University is currently expedition leader
for the ANSMET Program. More information on the expeditions can be found at:

http://www.cwru.edu/affil/ansmet/
Received on Fri 21 Jun 2002 02:05:35 PM PDT