Geology Reference
In-Depth Information
A77256 and 77257, respectively) continue to be of great
interest scientifically. The brachinite (ALH 84025;
Plate 48) has been steadily requested since 1984 but also
has received new interest with the discovery of the related
ungrouped achondrites GRA 06128 and 06129
(Figure 3.4; Plate 49). The two small angrites (LEW
86010 and 87051; Plates 53 and 54) have been requested
at steady levels because they are two members of the
small group of angrite meteorites and thus remain
essential to understanding the origin of angrites. The
lodranites (MAC 88177 and GRA 95209; Plate 41) were
highly requested when first found because there were so
few lodranites and acapulcoites in the 1990s. They have
remained of great interest because new samples are con-
tinuously being found and compared to these important
samples that originally helped to establish the groups.
160
140
120
100
80
60
40
20
1975
1980
1985
1990
1995
Year
2000
2005
2010
2015
Figure 3.3.
Requests for meteorites from the U.S. Antarctic
meteorite program since the beginning of the collection in 1978.
The peaks in 1983, 1997, and 2004 correspond to the announce-
ment of the first lunar meteorite (ALH A81005), the first meet-
ing after the announcement of possible fossil life in ALH 84001,
and the announcement of the first U.S. Antarctic nakhlite, MIL
03346, respectively.
3.2.6. Sample Handling, Preparation,
and Documentation
At JSC, the meteorite samples are prepared several
different ways and can be requested accordingly. Most
samples are prepared as chips, obtained either by use
of stainless steel chisels in a chipping bowl or using
rock splitters. Tools, sample containers, and bags are
made of stainless steel, aluminum, Teflon, or nylon.
Polyvials (polystyrene vials with polyethylene lids)
are also used as sample containers. In cases where a mete-
orite will be subdivided into many pieces for scientific
studies, the samples are cut dry in a GN2 cabinet with a
band saw, producing a 1- to 2-cm-thick slab. A listing of
meteorites that have been cut or slabbed at JSC is avail-
JSC-bandsawList.pdf.
More details about sawing and
possible effects on samples are at
http://curator.jsc.nasa.
the program (Figure 3.4). The Miller Range nakhlite
(Plate 74), in comparison, was found in 2004, with pairs
discovered in 2009, and it has already received more
than 100 requests (Figure 3.4). Interest in lunar meteor-
ites has also been sustained over decades with the MAC
88105 regolith breccia (Plate 68) receiving a steady
request rate over 25 years. The LaPaz Icefield (LAP)
02205 basaltic lunar meteorite (and its pairs) has
received the most requests of any lunar meteorite to
date (Plate 67). Small and rare lunar meteorites such as
QUE 93069 and EET 87521 (Plate 65) continue to
receive requests from the community; because they are
small samples and more precious, their allocation is
monitored closely by the MWG and MSG to preserve
material for future generations.
Several chondrites have received large numbers of
requests over the years and continue to provide impor-
tant materials for those studying primitive and early solar
system materials. For example, the CR2 chondrite GRA
95229 has been requested at a greater rate than others in
the past decade due to the diverse materials (presolar
grains, organics, chondrules, metals grains) found within
the CR2s [see
Weisberg and Righter
, 2014 (this volume);
Righter
, 2013] (Figure 3.4). Enstatite and other carbona-
ceous chondrites (CH, CO3, and CM1/2) are also heavily
requested as scientists examine the origin of organics,
zoned metal grains, and aqueous alteration on carbona-
ceous parent bodies (asteroids).
Finally, various achondrites have been heavily requested
over the years of the program, with some examples illus-
trated in Figure 3.4. The diogenites and ureilites (ALH
3.2.6.1. Cabinet processing: carbonaceous chondrites
and martian meteorites.
Since 1978, carbonaceous chon-
drites have had a dedicated cabinet for processing due to
the possibility that these samples contain unique organic
compounds. Since 1997, martian meteorites have been
processed in a dedicated cabinet (Figure 3.1, d), again
due to the possibility that there are organic or other
compounds that are specific to these samples, and to min-
imize the effects of handling under less clean conditions.
On occasion, an additional cabinet will be cleaned for
targeted processing of specific meteorites, such as lunar
meteorites.
3.2.6.2. Flow bench processing.
Three clean-room
laminar flow benches are used at JSC to process all other
samples (Figure 3.1, e), and also for initial processing of
new meteorites.
