Geology Reference
In-Depth Information
JSC (Houston, TX, USA), and the Smithsonian Insti-
tution (SI; Washington, DC, USA).
Samples from the subsequent two years (1977-1978
and 1978-1979 seasons) were collected jointly by the
United States and Japan, with the arrangement for the
division of samples set in place to cut samples >300 g in
half (cutting to take place at JSC) and then dividing sam-
ples <300 g on a one-by-one basis. Thin sections were
being made by the Smithsonian Institution of all of the
large samples, and JSC, SI, and NIPR received one sec-
tion from each meteorite. A subset of the smaller samples
(referred to then as “pebbles”) were classified by principal
investigators (PIs) as determined or recommended by the
Meteorite Working Group (MWG). For example, K. Keil
at the University of New Mexico proposed to help clas-
sify 145 of the small equilibrated ordinary chondrites
[
McGinley and Keil
, 1984]. Similarly, C. B. Moore (ASU),
M. Rhodes (UMass), J. Fitzgerald (Univ. Adelaide), and
S. J. B. Reed (Cambridge, UK) all received pebble-sized
samples [
Fulton and Rhodes
, 1984]. This approach was
not continued past this season, as it was not the most
efficient way to classify large numbers of samples.
A small number of samples from the 1977-1978 field
season were kept frozen, primarily for thermolumines-
cence studies. However, interest waned in keeping samples
frozen after this initial subset of samples; nonetheless, the
samples are stored frozen and remain available for study.
In the first few years of Antarctic meteorite handling at
JSC, the staff experimented with the idea of storing and
handling samples frozen, using a cold processing plate in a
cabinet, and using a cold storage room. Although some
hardware was assembled to do this, it became clear after
detailed tests that this was not an effective way to handle
samples due to the difficulty of keeping samples cold while
still allowing dexterity of the sample processor, length of
time required to process individual samples, and overall
expense. The cold processing approach was abandoned in
1979, after review and discussion by the MWG. At the same
time, JSC expanded their own thin-section-making labora-
tory to include meteorites (they were already making
Apollo
lunar sample thin sections). Also, realizing the importance
of minimizing contamination of organic compounds
contained in carbonaceous chondrites, processing protocols
were established for subdividing and handling carbonaceous
chondrites in a dedicated GN2 cabinet. The GN2 used for
all Antarctic meteorite handling and storage at JSC is of
high purity with levels not exceeding 20 ppm argon, 10 ppm
oxygen, hydrogen, carbon dioxide, carbon monoxide, and
moisture. Sample handling and processing techniques in the
meteorite lab at JSC were firmly established by 1980-1981.
The growth of the collection over the ensuing decades
posed new challenges and problems for the curation staff,
and the roles of staff at JSC and SI (Table 3.1) will be
highlighted where possible and relevant.
Table 3.1.
Curators associated with U.S. Antarctic meteorite
collection.
NASA Johnson Space
Center Curators
Smithsonian Institution
Curators
Donald Bogard, 1978-1984
Brian Mason, 1978-1987
James Gooding, 1984-1986
Glenn Macpherson, 1987-1996
Marilyn Lindstrom, 1987-2000
Tim McCoy, 1997-2007
David Mittlefehldt,
2000-2001
Cari Corrigan, 2008-present
Carl Allen, acting curator
2001-2002
Kevin Righter, 2002-present
3.2.1. Transport from McMurdo to Houston
Samples collected by ANSMET (U.S. Antarctic
Search for Meteorites program) teams are kept at
ambient conditions in isopods in the field and during
transport back to McMurdo, and then stored in freezers
at McMurdo Station (Crary Science Lab). The samples
are shipped to Port Hueneme, California, and then
transported to Houston, remaining frozen all along the
journey. The samples were flown to Houston until
approximately 1991, when they switched to truck trans-
port via frozen cargo trucks. The samples are kept
frozen in order to minimize interaction with water from
melted ice/snow within bags, and also to prevent rusting
that might be accelerated at room temperatures.
3.2.2. Staging
Once samples arrive in Houston they are immediately
transferred into one of two freezers in the Antarctic
Meteorite Processing Lab (MPL) at JSC, a class 10000
cleanroom with HEPA filtered air handler system that
effectively makes the cleanroom operational at Class
1000 or better. The newly arrived samples are tempo-
rarily stored in the freezers which are set at −10° to −4°
F (-23 to -20 °C). Storage under frozen conditions allows
them to remain in their collected state until the processing
personnel are ready to study them under the controlled
conditions of the processing lab. Samples are assigned a
random five-digit number in the field and are renum-
bered at JSC and given their official name, a three-letter
prefix abbreviating the geographical area in which they
were found, followed by two digits for the collection year
(being the year the team began the field season), followed
by a three- or four-digit number uniquely identifying the
sample from that season (i.e., “ALH 84001” for Allan
Hills 84001 or “MIL 090001” for Miller Range 090001).
Four digits must be used for collection years in which
greater than 999 samples have been recovered from
one area. These are dense collections areas; therefore,
