Geology Reference
In-Depth Information
Antarctic Research Expedition (JARE-10) was one of
several glaciologists establishing a network of survey
stations in the East Antarctic ice sheet to allow the study
of glacial movement. As they extended their survey across
a blue icefield uphill from the Yamato (Queen Fabiola)
Mountains, they found a total of nine meteorite speci-
mens [
Yoshida et al.
, 1971;
Yoshida
, 2010). Within a few
years, mounting numbers of meteorite recoveries by the
Japanese eventually convinced the United States Antarctic
Program (USAP) to begin supporting active searches, as
described in chapter 1 [
Marvin
, 2014 (this volume)].
As of this writing, ANSMET has recovered more
than 20,000 meteorites, but these numbers account for
only part of the program's success. Consistent initial
characterization of recovered specimens, curation at the
highest level, and rapid, cost-free availability have given
ANSMET meteorites unique value within the planetary
materials research community, as described in chapter 3
[
Righter et al
., 2014 (this volume)].
The early successes of the U.S. Antarctic meteorite
program quickly led to increasing demand for new spec-
imens and to the well-supported, institutionalized pro-
grams of recovery in place today. With a strong backbone
of aerial logistics, U.S. expeditions have ranged widely
across Antarctica, predominantly in East Antarctica
along the Transantarctic Mountains. ANSMET has
been one of the most active governmentally-supported
meteorite recovery programs, with 45 independent
field parties deployed to more than 75 different sites
during 36 seasons of fieldwork (Figure 2.1 a through e).
Continued demand for specimens recovered by ANSMET
has been the primary driver for annual field parties,
which are enabled by improvements in remote sensing of
polar regions, an increased understanding of meteorite
concentrations, and better access to remote locations.
The fieldwork has evolved with these changes, resulting
in a field program that is highly adapted to available
logistics and the needs of the planetary materials
community. This chapter documents the field practices
that have helped ANSMET support research through
the past four decades.
with durations ranging from as many as six seasons to as
few as one. Grant proposals may request support for field
seasons dedicated to systematic meteorite recovery from
known sites (hereafter called a systematic activity), recon-
naissance efforts dedicated to improving our under-
standing of poorly known or previously unvisited sites
(hereafter called a reconnaissance or recon activity), or
some combination of these. A typical proposal will there-
fore include a list of sites prioritized from among poten-
tial targets based on our understanding of each site's
potential. The highest-priority fieldwork targets are, not
surprisingly, those we think will yield the most meteorite
specimens. However, this is typically based on prior expe-
rience at the site, which is always incomplete during early
visits. More practical issues such as logistical availability
can trump potential meteorite yield. For example, when a
remote helicopter camp allows us to reach otherwise
inaccessible locations, those targets become a higher pri-
ority; and when aircraft support is predicted to be limited,
we may choose targets demanding fewer flight hours.
Recon and systematic targets are both mixed into the
long-term plan; the former typically result in fewer mete-
orite recoveries but are essential to ensure a continuous
supply of new specimens. On a few occasions we have
also adjusted the recon/systematic activity mix to reduce
stress on the curatorial system, favoring recon activities
when a characterization backlog is growing. The desire
for geographical separation between ANSMET field
parties (to minimize the effects of individual weather sys-
tems) is also considered. Every ANSMET proposal also
includes alternate targets for either style of activity,
allowing the project to adjust to rapid changes in USAP
logistics and programmatic issues.
Meteorite concentration sites tend to occur on exposed
blue ice in a variety of specific geographical and glacio-
logical settings; the characteristics of these icefields and
meteorite concentration mechanisms are discussed in
detail in
Harvey
[2003]. Identification of such sites through
examination of maps and imagery has been a natural first
step in ANSMET's work since the program began. USAP-
produced topographic maps and aerial photography doc-
umenting much of the Transantarctic Mountains became
available throughout the 1960s and 1970s, and during
ANSMET's early years these served as a primary means
for identification of meteorite concentration sites. These
maps, however, were primarily meant to serve naviga-
tional and geological needs, and do not document blue
ice. Similarly, while aerial photography coverage was
excellent, many blue ice areas were visible only in low-
angle oblique images that mask their full extent. The most
powerful “remote sensing” tool employed by ANSMET
in this era was opportunistic reconnaissance flights, dur-
ing which field personnel would sit glued to the windows
of an aircraft, annotating maps and photographing key
2.2.2. Preseason Planning and Site Selection
U.S. activities in the Antarctic are carried out within
the U.S. Antarctic Program (USAP), funded and
managed by the Office of Polar Programs (OPP) of the
National Science Foundation. During its history,
ANSMET has been supported through USAP, both
directly (through OPP grants) and indirectly (through
logistical support funded by NASA). As a result, planning
for any given season may begin as many as seven years
before deployment (at the time a grant is funded). Grants
supporting ANSMET have been competitively selected,
