Geology Reference
In-Depth Information
snowmobiles, so they were obliged to take turns trudging
to each rock, carrying the camera and collecting equip-
ment, and then carrying each wrapped-up stone back to
the camp to be stored in the shipping box.
1.7.1. Early Procedures at Johnson Space Center
Many of the meteorites had ice or snow on them when
they were collected, so at JSC each new specimen was put
into a glove box in a stream of dry nitrogen to be thawed
and dried and then sawed with a clean blade, or chipped
apart depending on its size. It was photographed at each
step of its processing. Three chips for thin sections were
taken from each specimen that weighed more than 100 g.
The sections were cut and polished at the Smithsonian in
Washington for distribution to Japan, and to libraries
at the NASA Johnson Space Center in Houston and the
Smithsonian's Natural History Museum in Washington.
The mineralogy of each thin section was described by
Brian Mason, who, as noted above, had volunteered for
the job. At the earliest meeting of the MWG in Houston,
Klaus Keil raised the question of who would describe all
these thin sections. He didn't want to do it himself, and he
didn't want his students to spend time that way, either.
But Brian, knowing that this question would arise, had
given me a copy of one of his succinct descriptions of a
thin section to read out to the members. Keil relaxed,
seeming fully satisfied. Brian, during his long career of
field and laboratory investigations, and his writing of
topics on geochemistry and meteorites, had developed a
quick and effective technique of identifying meteorites in
thin sections. He said later that he had had a wonderful
time going through the several thousand new thin sec-
tions of Antarctic meteorites. And he was pleased that
this was recognized as the essential service it was.
Each specimen unpacked at JSC was assigned a unique
label. The labels had been worked out by the MWG in
discussions with the Committee for Nomenclature of the
Meteoritical Society. Each label would begin with three
letters identifying its location, followed by the letter A,
followed by two digits indicating the year of its discovery,
and three more digits indicating the sequence in which
the specimen was opened at JSC (not when it was found
in the field). For example, ALH A78362 designated the
following: Allan Hills, Expedition A, 1978, the 362nd
to be opened at JSC. “Expedition A” was adopted at
the insistence of Paul Pellas, the member from France,
who insisted that many countries might begin sending
collecting expeditions each year and would need differ-
ent expedition letters. The MWG agreed to assign new
letters whenever additional expeditions were fielded in
a given year, but this never came to pass, so the letter A,
which had been part of every label since 1975, was
dropped in 1982.
Figure 1.3a.
A chondrite, about 4.5 billion years old, that fell so
recently that it broke into two pieces when it struck the ice.
Figure 1.3b.
An achondrite, ALH A81006, a polymict breccia
likely from the surface of asteroid 4 Vesta (Plate 57), that has
been carried within the moving ice for perhaps several hundred
thousand years before appearing at the surface.
NASA's curatorial facility at JSC had supplied the field
crews with all the newly cleaned equipment they needed for
collecting specimens without touching them. Sometimes
nicknamed “
Apollo
surplus,” this included teflon bags,
stainless steel tongs, and teflon tape designed for use at sub-
zero temperatures. Each specimen was placed in a Teflon
bag and then that bag was dropped into a second bag
carrying a numbered aluminum tag. The second bag was
then sealed shut. In order to maintain the specimens at sub-
zero temperatures while they were being stored and shipped,
NASA provided the teams with burglar-proof padded steel
boxes measuring about 60 × 60 × 90 cm. One of these boxes
was brought to the camp site at the Allan Hills.
The harvest of meteorites in that season was acquired
under especially trying circumstances: the team had no
