Geology Reference
In-Depth Information
1
The Origin and Early History of the U.S. Antarctic Search
for Meteorites Program (ANSMET)
Ursula B. Marvin
The information that would first lead U.S. teams to
search for meteorites in Antarctica was presented at an
evening session of the Meteoritical Society on 27 August
1973 in Davos, Switzerland. On that occasion, Dr.
Makoto Shima of the Institute of Physical and Chemical
Research of Japan described four meteorite fragments
with differing mineralogical and chemical compositions
that had been collected in 1969 from a downhill sloping
patch of bare ice in the Yamato Mountains of eastern
Antarctica.
In the audience sat William A. Cassidy, of the University
of Pittsburgh. Bill Cassidy wrote later that, on hearing
that report a comic-strip lightbulb appeared in his mind
with a message reading: “Meteorites are
concentrated
on
the ice!” To him, this was a new and electrifying idea.
Cassidy expected the whole room to be excited, but looking
around he found the audience looking as comatose and
glassy-eyed as audiences sometimes do. I was chairing the
session that evening, but I was much too preoccupied
with keeping the speakers more or less on schedule to be
having any eureka experiences.
After the session, Cassidy talked with Dr. Shima and
his wife, Dr. Masako Shima, both of whom are chemists
who were then visiting the Max-Planck-Institut für
Chemie in Mainz. Dr. Shima explained to Cassidy that
the team of glaciologists in the Yamato Mountains had
collected five more meteorites from the same patch of ice.
Of the nine meteorites, only the four they had reported
on had been analyzed for their chemical compositions
and rare gas contents. These had been identified as (a)
an enstatite chondrite, (b) a Ca-poor achondrite, (c) a
probable carbonaceous chondrite, and (d) an olivine-
bronzite chondrite. The remaining five also clearly were
meteorites of differing types. Earlier that summer the
Shimas had coauthored an article about the four ana-
lyzed meteorites with Dr. Heinrich Hintenberger of
Mainz, in
Earth and Planetary Science Letters
[
Shima
et al.
, 1973], and the Shimas also had published a brief
summary of their chemical results in the abstract volume
of the meeting at Davos [
Shima and Shima
, 1973]. But
Cassidy had not seen the article and had skimmed too
quickly through the abstracts.
At the meeting, Cassidy was captivated by the evi-
dence that meteorites from different falls sometimes are
concentrated by the dynamics of ice motion. Within the
hour, he began planning a proposal to the National
Science Foundation's Division of Polar Programs to
lead an expedition to search for meteorite concentra-
tions on patches of ice in Antarctica. He assumed that
the concentration in the Yamato Mountains could not
be unique in a huge continent making up 9% of the
Earth's land surface, so he would propose to work out
of McMurdo Station, the U.S. base that lies near the
opposite edge of Antarctica from the Yamato Mountains
(Figure 1.1).
1.1. HISTORY OF METEORITE FINDS IN
ANTARCTICA
Cassidy was well aware of the historical record of
random meteorite finds in Antarctica, in which only four
meteorites had been encountered since 1912. In that year,
Douglas Mawson led the Australian-Antarctic Expedition
on a five-year study of the Adelie Land coast. Mawson's
three-man party discovered a stony meteorite lying on
hard snow on their fourth day after breaking camp.
That stone, Adelie Land, was the only known Antarctic
meteorite for the next 50 years. Then, soon after the
International Geophysical Year (July 1957-December
1958) had generated a widespread interest in Antarctica,
