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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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