Geology Reference
In-Depth Information
1e+6
1e+5
1e+4
1e+3
1e+2
CV3
C03
CR1
CR2 and CR3
CM1, CM2, C2
Cl and C1
Typical blank levels 10-20 ppb
1e+1
Apollo 17 lunar soil - 5 ppb from terrestrial
1e+0
Curation UPW < 0.1 ppb
1e-1
CV3
C03
CR1
CR2
CR3
CM2C2CM1
Cl
C1
Carbonaceous chondrite type
Figure 3.5.
Summary of amino acid measurements made on Antarctic carbonaceous chondrites, compared to levels of amino acids
measured in Apollo samples [
Brinton and Bada
, 1996], in UPW [
Bada et al
., 1998], and blank levels measured during amino acid
measurements [
Bada et al
., 1998]. All carbonaceous chondrite data are from
Glavin et al
. [2006, 2011, 2012],
Glavin and Dworkin
[2009],
Burton et al
. [2012], and
Martins et al.
[2007].
hot UPW rinse for cabinets, tools, and other items. The
total organic content of the UPW system is checked reg-
ularly and is typically near 10 ppb.
The Antarctic meteorite lab was designed as a Class
10,000 lab (ISO 7), at which it operated through early
2001, until HEPA filtered air and a new air handler unit
was installed. The lab also has an air shower in its
entrance, which takes air from the main room, passes it
through a HEPA filter, and then recycles it within the
shower. The purpose of the recycling is to remove any
loose dirt from the gowning process in the change room,
which potentially stirs up particles. This design has
undoubtedly led to a cleaner environment. Particles that
are >0.5 microns are kept to low levels, and this effec-
tively cuts out mold, fungi, pollen, human hair, algae, and
dusts. Since the installment of the HEPA filtered air
system, particle counts in the various processing areas of
the MPL have been consistently between 100 and 1000
counts.
The curation practices have led to a clean environment,
and it is periodically monitored with testing of air, water,
and glove boxes. For example, studies of the organic com-
pounds in the meteorite lab main room and the martian
meteorite cabinet revealed the presence of low levels of
siloxanes, which can be from sealants, or lubricants in
motors, or elastomers in gaskets. Small amounts of
fluorocarbons detected in the meteorite room air may
be derived from refrigerants. Isopropanol, butanol,
propoxypropanol, 2-butoxyethanol, butoxypropanol,
dipropylene glycol, found in the room sample may be
from solvents. Finally, aromatic compounds such as
toluene, ethylbenzene, xylenes, alkylbenzenes, and low to
medium boiling hydrocarbons are also used in solvents.
None of these species or the levels at which they are pre-
sent have been of concern to investigators who study
meteorite samples, but knowledge of their presence is
very important.
There are also concerns about some materials used
during curation, and some examples are given here. For
example, in some cases water can pyrolize nylon and
produce an amino acid contaminant [
Shimoyama et al
.,
1985]; use of Teflon bags can eliminate this problem
[
Glavin et al
., 2006]. Heat sealing of bags can produce
caprolactum, a monomer used in the production of
Nylon 6; most cabinet processing uses heat sealing to seal
storage bags, so it is important to know about the presence
of this compound. Cabinet gloves can offgas various
species such as CO (butyl rubber), isopropyl alcohol and
C10-C14 hydrocarbons (viton), COS (neoprene), and
SO
2
(hypalon) [
Righter et al
., 2008], so gloves can be
selected accordingly; the JSC Antarctic meteorite lab has
used neoprene gloves. Fabrication and construction of
processing cabinets (or other equipment) can utilize
lubricants and other chemicals; an example is xylan, a
complex amide, used in JSC processing cabinets in the
1980s; discovery of this material in cabinets led to elimi-
nation of the use of xylan in early 1990s [
Wright et al.
,
1991, 1992].
