[meteorite-list] The Antarctic Meteorites: Classification and Curation at the Smithsonian Institution

[Shawn Alan]

Morning Listers, 

Here is an article from the 41 Lunar and Planetary Science Conference about the Smithsonian and the challenges they face on the large numbers of meteorites they have to classify from Antarctic. 
 
 The Antarctic Meteorites: Classification and Curation at the Smithsonian Institution. C. M. Corrigan1, L. C. 
Welzenbach1, T. J. McCoy1, 1 Department of Mineral Sciences, National Museum of Natural History, Smithsonian 
Institution, Washington, DC 20560-0119, USA; corriganc at si.edu. 
 
A Relentless Onslaught: Over the past decade, 
we have classified between 450-1000 Antarctic mete-
orites per year (Figure 1). This pace, and the variabili-
ty in staffing levels in the Antarctic Meteorite Program 
over the past ten years, has caused us to make a few 
changes at the Smithsonian. We have now entered a 
period of relative stability following the hire of the 
author (Corrigan) who has been tasked with managing 
the day-to-day activities of the Antarctic meteorite 
collection. In addition, we have implemented some 
improvements aimed at both saving time and creating a 
more robust classification process. The first of these 
includes a “first-pass” classification during initial han-
dling at the Smithsonian, during which we give a pre-
liminary grouping to each meteorite (ordinary chon-
drite, carbonaceous chondrite, achondrite) which al-
lows us to separate out those unique types that will 
need to be sectioned right away. This initial classifica-
tion is then confirmed or refuted using a variety of 
techniques. These include further visual examination 
with binocular microscopes for all meteorites, oil im-
mersion of a few olivine grains for equilibrated ordi-
nary chondrites, and thin section examination and mi-
croprobe analyses for other types of meteorites (carbo-
naceous chondrites, enstatite chondrites, achondrites, 
iron meteorites and “unknowns”, which are occasio-
nally found to be terrestrial samples from Antarctic 
glacial moraines). Our goal is to have all of the An-
tarctic meteorites classified within two years of their 
return from the ice, a standard now codified in a U.S. 
Federal Regulation on Antarctic meteorites. In this 
context, newly collected meteorites have always ar-
rived before all the previous year’s meteorites have 
been classified. 
Reducing Complexity while Maintaining Objec-
tivity: A significant challenge to timely classification 
is simplifying the process by comparing meteorites 
from a single field area. Pairing groups are common 
and classification can be accomplished more quickly if 
focus is maintained on a single field area. This has 
been increasingly challenging during the past few 
years, with multiple field parties working in several ice 
fields returning meteorites from many geographically 
and glaciologically distinct areas in a single year. 
While the meteoritics research community tends to 
subdivide groupings and attach significance to abun-
dances of different groups, the classifications we com-
plete must have a level of robustness that is consistent 
and can be maintained. As examples, we avoid sub-
classifying eucrites and while we attach both chemical 
groups and petrologic types to ordinary chondrites 
classified with only visual examination and oil immer-
sion, we advise due caution in overinterpreting abun-
dances within these groups. While the overall percen-
tage of ordinary chondrites is probably a robust statis-
tic, comparing abundances of L5 vs. LL4 is fraught 
with peril. 
Curation of the Antarctic Meteorites: The 
meteorites that are returned from Antarctica are, in the 
long term, stored and curated by the staff at the Smith-
sonian. On hand (and onsite at the National Museum 
of Natural History, NMNH), we house a chip of each 
meteorite returned from the ice and the reference thin 
section (those used in the initial classification) of each 
meteorite of significant scientific interest to the mete-
orite community. All Antarctic meteorites are even-
tually sent from the Johnson Space Center (JSC) to the 
Smithsonian for indefinite curation. Exceptions to this 
rule are those meteorites of intense scientific interest to 
the community (i.e., those that receive a large number 
of requests for sampling for research projects from the 
community). These meteorites, which include those 
on the Meteorite Working Group’s “special list” (a list 
of rare/small designed to prevent the over-allocation of 
any individual meteorite), are housed and allocated 
from the specialized facilities at JSC. Meteorites are 
transferred to the Smithsonian Institution permanently 
after three years without requests by the scientific 
community and become the responsibility of the SI for 
future allocation. At the Smithsonian, meteorites are 
housed in a special facility designed for the long-term 
curation of meteorites (Figure 2). That facility, which 
is fashioned after the Meteorite Processing Lab at 
Johnson Space Center, includes stainless steel nitrogen 
atmosphere cabinets for the storage of meteorites along 
with a larger, updated facility currently under con-
struction. At the current rates of collection, this facili-
ty should be sufficient to house incoming samples for 
approximately 20 years. This new facility will also 
house the meteorites in a “Class 10,000” clean room. 


The Science of Antarctic Meteorites: Overall, 
our job is to provide a preliminary classification of 
each meteorite that ANSMET recovers and returns, not 
to answer the individual compelling scientific ques-
tions surrounding each meteorite, no matter how tanta-
lizing the meteorite may be. Our overarching goal is 
to provide the Antarctic meteorite material to the 
scientific community in a timely fashion, with suffi-
cient information that individual researchers can re-
quest the samples that will most benefit their research. 
Sample Requests and Education: Sample Re-
quests: Twice a year the newly classified Antarctic 
meteorites are announced in the Antarctic Meteorite 
Newsletter [2]. Request deadlines are included in the 
Newsletter (and are generally about a month after its 
publication) as is the link to the sample request form. 
The Meteorite Working Group (MWG) meets bian-
nually as well, usually in Houston the weekend after 
the LPSC and sometime in September at the NSF 
Headquarters in Arlington, VA. All requests for An-
tarctic meteorites that are not considered “curatorial” 
are processed at these meetings and allocations are 
completed following the meetings. “Curatorial” re-
quests (includes iron meteorites and those samples that 
have been permanently transferred into the SI collec-
tion) are currently being dealt with individually by the 
SI and/or JSC, and many of those are dealt with on a 
rolling basis. Additionally, MWG is reviewing some 
requests via email between meetings. 
Education: In addition to samples being allocated 
for research purposes, we also provide samples for 
education and public outreach. Many PIs request and 
receive samples from the SI collection that are availa-
ble for use in exhibits. Suites of samples have been 
put together for classes on meteorite petrology by JSC 
and should be requested through the education sample 
curator there (currently Mary Luckey). These can be 
of immense importance to graduate students who may 
otherwise come out of graduate school having seen 
only the types of meteorites they work on, or only 
spectra of other bodies that may (or may not!) relate to 
the actual rocks we have in our collections. Ground 
truthing these samples, and putting them into perspec-
tive with other material from throughout the Solar Sys-
tem is a hugely beneficial exercise. 
Finally, individual researchers are welcome to 
come view thin sections within the SI collection at any 
time. We have the facilities for viewing and photo-
graphing the library sections for the Antarctic Mete-
orites. Many individuals have found it invaluable to 
sit and spend a few days looking at all of the sections 
of one particular type of meteorites, for example. 
References: [1] Corrigan C.M. et al. (2008) Work-
shop on Antarctic Meteorites: Search Recovery and 
Classification, MAPS 43 Suppl., A180. [2] http://www-
curator.jsc.nasa.gov/antmet/amn/amn.cfm 
 
http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2332.pdf
 
Shawn Alan