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Natural
Thermoluminescence Survey of Antarctic Meteorites |
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Thousands of meteorite fragments have
been found on blue ice fields in Antarctica over the past two decades and more
continue to be found each year by research teams from the United States,
Japan, and Europe. The natural thermoluminescence (TL) laboratory's primary
purpose is to provide data on newly recovered Antarctic meteorites that can
be included in discovery announcements and to investigate the scientific
implications of the data. Natural thermoluminescence is light that is emitted
from a sample during heating at low temperatures, typically less than 400 C.
This light reflects energy stored in certain minerals, notably the mineral
feldspar in most meteorites and lunar samples, this energy coming from
ionizing radiation that has passed through the minerals. We have obtained TL
data for over 1100 Antarctic meteorite fragments. The natural TL database
comprises all of the data generated by the Cosmochemistry Group as of
November 1998. Natural TL levels of meteorites are indicators of recent
thermal history and terrestrial history and the data can be used to study the
orbital/radiation history of groups of meteorites or to study the processes
leading to the concentration of meteorites at certain sites in Antarctica. An
important application of these data is the identification of fragments, or
"pairs" of meteorites produced during by breakup of meteorites
during atmospheric passage or during terrestrial weathering.
Thermoluminescence data are particularly useful for pairing within the most
common meteorite classes, which typically exhibit very limited petrographic
and compositional diversity. Although not originally part of the laboratory's
objectives, TL data are also useful in the identification and classification
of petrographically or mineralogically
unusual meteorites, including unequilibrated
ordinary chondrites and some basaltic achondrites.
In support of its primary mission, the laboratory also engages in TL studies
of modern falls, finds from hot deserts, and terrestrial analogs. A summary
of some of these projects may be found on our natural TL page.
The natural TL survey laboratory is run by Dr. Paul H. Benoit and Dr. Derek
W.G. Sears. Samples are provided by the Meteorite Working Group of NASA,
Johnson Space Center. The laboratory is jointly funded by NASA and the
National Science Foundation's Division of Polar Programs. |
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