Kevin Righter, NASA-JSC
This newsletter reports 234 new meteorites from the 2014, 2015, and 2016 ANSMET seasons from the Dominion Range (DOM 14), Miller Range (MIL 15), and Elephant Moraine (EET 16) areas. Meteorites include a IIIAB iron, an L chondrite impact melt, a lodranite (?), and 6 unequilibrated ordinary chondrites. We also reclassified a number of meteorites (see below) and remind requestors that some of our samples are small and rare and require stronger than usual justification when submitting a request (also see below).
Requesting small and special samples
The US Antarctic meteorite collection has many rare samples that are preserved for scientific study. Many of these samples have been in the collection since the first years of the program, and have less material available for study. Others are simply small, and there is limited material available. Finally, some have been disaggregated during sample preparation and handling due to their degree of weathering, fracturing, and overall physical state. These samples will be preserved as best as possible, which also means that not all requests can be honored. For severe cases, sample requests may be rejected to save material for future studies of the most compelling nature. For example, requests for multiple members of a meteorite group as part of a cursory survey are unlikely to be honored for samples of this small and rare nature. This message is simply a reminder that requestors should do the necessary background research on such samples to ensure that their request has as much specific justification as possible. Resources for obtaining information about our samples include the Antarctic Meteorite Newsletters, our online database, and the online bibliography which lists over 1600 peer reviewed publications through 2017:
In addition, detailed information is available in our sample compendia:
Reminder to Sign and Return Your Annual Inventory
US Antarctic meteorite inventories were mailed to all PIs in November 2017. You received a list of samples with a header at the top for two signatures — one for you (the PI) and one for an institutional official. Thanks to all of those who have returned their inventories to us, but if you haven't already, please follow these instructions:
- Print the list
- Compare your sample list to samples in your possession
- Confirm samples are in your possession unless consumed during research (if approval was obtained during original sample request), and note any discrepancies
- Sign/date top of first inventory page
- Institutional official must sign/date top of first page
- Scan and email it back to us (JSC-ARES-MeteoriteRequest@nasa.gov)
PIs that do not respond to inventory queries by the NASA Curator will not receive samples from the collection.
Reminder to acknowledge samples received from NASA-JSC
When publishing results of your research, please include the split numbers used in the research. We also request that scientists use the following acknowledgement statement when reporting the results of their research in peer reviewed journals: "US Antarctic meteorite samples are recovered by the Antarctic Search for Meteorites (ANSMET) program which has been funded by NSF and NASA, and characterized and curated by the Astromaterials Curation Office at NASA Johnson Space Center and the Department of Mineral Sciences of the Smithsonian Institution." Such an acknowledgement will broaden the awareness of the funding mechanisms that make this program and these samples possible.
We suggest you find out how to acknowledge samples received from all the collections/museums from which you have received materials so that all the institutions making samples available to you receive proper credit and acknowledgement.
1) Reclassification of PCA 82500 currently a CK5, but should be a CK3. The observations supporting the low petrologic grade include (1) lack of ilmenite exsolution from magnetite, a property typically seen in type 3 CKs and (2) olivine zoning observed in BSE within the largest chondrule in the type section. Taken together, these suggest classification as a type 3.
2) Reclassification of various unusual carbonaceous chondrites
The compositional, mineralogical, and petrological characteristics of a number of carbonaceous chondrites in our collection has been recognized by our PIs. To draw a distinction between these samples and the more standard members of their groups, we have reclassified the following samples due to observations made by Davidson et al. (2015) and Floss and Brearley (2014) for MIL 07687, and by Choe et al. (2010) for all the rest:
DOM 03238 : CO3 chondrite (anomalous) (Choe et al., 2010)
EET 90043 : CO3 chondrite (anomalous) (Choe et al., 2010)
MIL 07687 : C2 chondrite ungrouped (Davidson et al., 2015; Floss and Brearley, 2014)
GRA 98025 : C2 chondrite ungrouped (Choe et al., 2010)
GRO 95566 : CM chondrite (anomalous) (Choe et al., 2010)
LEW 85311 : CM chondrite (anomalous) (Choe et al., 2010) (paired with LEW 85306, 85307, 85309, and 85312)
PCA 91008 : CM chondrite (anomalous) (Choe et al., 2010)
QUE 99038 : CM chondrite (anomalous) (Choe et al., 2010)
WIS 91600 : CM chondrite (anomalous) (Choe et al., 2010) (paired with WIS 91608)
Choe, W. H., Huber, H., Rubin, A. E., Kallemeyn, G. W., & Wasson, J. T. (2010) . “Compositions and taxonomy of 15 unusual carbonaceous chondrites. ” Meteoritics & Planetary Science 45, 531-554.
Davidson, J., Nittler, L. R., Stroud, R. M., Takigawa, A., De Gregorio, B. T., Alexander, C. M., ... & Cody, G. D. (2015) . “Organic matter in the unique carbonaceous chondrite Miller Range 07687: a coordinated in situ NanoSIMS, FIB-TEM, and XANES study. ” 46th Lunar and Planetary Science Conference, Abstract # 1609.
Floss, C., & Brearley, A. J. (2014) . “Presolar grain abundance variations in the unique carbonaceous chondrite MIL 07687. ” 77th Annual Meeting of the Meteoritical Society, Abstract # 5183.
3) Reclassification of equilibrated ordinary chondrites
A) MAC 88122
This sample was originally announced as an LL5 chondrite in newsletter 13, number 2 (March 1990), and then reclassified as an L/LL5 chondrite in newsletter 30, number 2 (August 2007). The 2007 reclassification was a mistake – we find no evidence for the L/LL classification, and thus re-classify this sample back to its original LL5 classification based on the olivine content (Heggy et al., 2012, Icarus 221, 925-939) and the Ni and Co content of the metal (Table of reclassifications from AMN 30, no. 2, data provided by Welten and Nishiizumi in 2007).
B) GRO 85 and 03 samples
The ANSMET 2003-2004 field team recovered meteorites from the Grosvenor Mountains region of the TransAntarctic Mountains. Within this area was a small collection of ~80 meteorites that appeared to be pieces of the same fall, based on their weathering state, hand specimen appearance, and the fact that they were found in a narrow ellipse with a long axis of 1.7 km, with the largest fragments at one end (Kress et al., 2007).
Subsequent classification of these samples included a wide range of chondrites including LL, L and H, but detailed chemical analyses of 6 larger specimens from the field yielded metal content and composition consistent with H chondrite samples (Welten et al., 2009) . Because of the discrepancy between the original classification and the subsequent studies, and the fact that this small strewnfield may be of special interest to meteoriticists, we have measured the magnetic susceptibility of all samples from this proposed strewnfield. The results indicate that most are indeed H chondrites, and we present the full dataset here, and propose re-classification of those that were classified previously as L or LL, as indicated in the table. Values > 4.8 are consistent with H chondrites, and those < 4.5 are consistent with LL chondrites. After reclassification, only two remain that are consistent with L chondrites (GRO 03005 and GRO 03036), and there are no LL chondrites.
Welten, K. C.; Nishiizumi, K.; Caffee, M. W.; Leclerc, M. D.; Jull, A. J. T. (2009). “Cosmogenic Radionuclides in Chondrite Shower from Otway Massif. ” 40th Lunar and Planetary Science Conference, (Lunar and Planetary Science XL), held March 23-27, 2009 in The Woodlands, Texas, Abstract # 1488.
Kress, M. E.; Benedix, G. K.; Schutt, J.; Harvey, R. P. (2007) . “An Unusual Strewn Field at the Otway Massif, Grosvenor Mountains, Antarctica. ” 70th Annual Meteoritical Society Meeting, held in August 13-17, 2007, Tucson, Arizona. Meteoritics and Planetary Science Supplement, Vol. 42, Abstract # 5270.
Grosvenor Mountains 85 and 03 Sample Reclassifications
|Sample||M0 (10-3 )||Mass (g)||Log χ (10-9 m3/kg)||AMN Classification||New Classification|
C) DOM 85 and 03 samples
The Dominion Range has been visited by ANSMET teams during the 1985-86, 2003-04, 2008-09, 2010-11, 2014-15 seasons. A large ordinary chondrite shower dominates the collection in this area. Initial characterization of the samples was yielding ~60% LL chondrites. Several years ago we began to suspect this classification because we weren't seeing any LL chondrite in random thin section sampling, and targeted microprobe analysis of 15 LL chondrites from the DOM 08 and DOM 10 season revealed they are actually L chondrites. We decided a systematic reclassification of this field is necessary to have accurate statistics. In the continued efforts to reclassify, we report magnetic susceptibility data for 142 samples from the 2003-04 and 1985-86 seasons. As suspected, the majority of these samples are L chondrites, with very few LL chondrites. The samples requiring reclassification are indicated in the table as well. Values > 4.8 are consistent with H chondrites, and those < 4.5 are consistent with LL chondrites.
Dominion Range 85 and 03 Sample Reclassifications
|Sample||M0 (10-3 )||Mass (g)||Log χ (10-9 m3/kg)||AMN Classification||New Classification|
ANSMET 2017-2018 Field Season
Jim Karner, Ralph Harvey and John Schutt
Case Western Reserve University
The 2017-18 season included both reconnaissance and systematic work. The season started on Dec. 12, 2017 as a group of eight (see pic) plus gear flew to Shackleton Glacier Camp (SHG), which was situated in the southern Transantarctic Mountains. Once at SHG the group split into two teams of four (i.e., Team A and B) and proceeded to be shuttled to their respective work sites by Twin Otter. Team A, consisting of Jim Karner, Brian Rougeux, Barbara Cohen and Julianne Gross conducted systematic searches of the Mt. Cecily/Mt. Raymond (MC/MR) icefields in the Grosvenor Mountains. The area had been visited in 1995-96, but plenty of unsearched ice remained. The MC/MR area was visually stunning with its huge rolling seas of blue ice at the bases of the mountains and nunataks, but it was really, really cold. And windy. Most days the temps were below zero (F) or just slightly above that- and the winds constantly blew at 15 knots or greater. Team A spent a total of 34 days at MC/MR, and despite the tough conditions recovered a total of 211 meteorites. The bulk of the meteorites were found by snowmobile sweeps of the large icefields, but several dozen were also found by meticulous foot-searching of the many and heavy moraines in the area.
2017-18 ANSMET team: (l-r) Scott Van Bommel, Jim Karner, James Day, Juli Gross, Barbara Cohen, Brian Rougeux, John Schutt, Ioannis Baziotis
The reconnaissance team (Team B) consisted of John Schutt, James Day, Scott Van Bommel, and Ioannis Baziotis. The team worked in the Amundsen Glacier region and evaluated six bare ice areas for potential meteorite concentrations. Their first stop was the Mt. Wisting and Mt. Prestrud area, which was first visited in 1995-96. The team spent just a few days in the area and recovered about ten meteorites through both snowmobile sweeps and moraine searching. The next move took the team to Nodvedt Nunataks, where they recovered forty meteorites; their final move took them to the Amundsen Glacier icefield where one possible meteorite was collected. Team B also spent a day performing helicopter reconnaissance of two relatively small bare ice patches in the region. The helos transported the team to both the Upper Amundsen Glacier and Devils Glacier icefields where quick foot-searches of the ice were performed. Two meteorites were recovered from the Devils Glacier ice while no rocks (of any kind) were even seen on the ice at Upper Amundsen! In summary, the reconnaissance team evaluated six bare ice areas for meteorite concentrations. Two of the sites had been previously visited (Mt. Wisting and Mt. Prestrud), but the others were first visits. A total of 52 specimens were recovered, but no significant meteorite concentrations were realized.
Report from the Smithsonian
Cari Corrigan, Geologist (Dept. of Mineral Sci.)
New laboratory staff member Rob Wardell
Things continue to evolve and adapt as necessary in the Division of Meteorites at the Smithsonian. Our new microprobe (a JEOL JXA 8530f+ Hyperprobe) is still running beautifully, and it is a good thing! Our SEM EDS detector hit a major snag, rendering it useless since the holidays. It is now the instrument we use to classify the Antarctic equilibrated ordinary chondrites, so that left us with a bit of a problem. Never fear, the Hyperprobe is here! We were able to use its state of the art capabilities to perform the EDS analyses generally the same way as we do on the SEM. Therefore, we bring you the entire newsletter with data obtained using the new instrument. Tada! It was a lot of fun figuring out how to make it happen (despite the struggles due to our learning curve)! In personnel news, we have hired another member to our laboratory staff. We would like to welcome Rob Wardell to the crew! Rob comes to us with an engineering degree and a lot of great lab experience. We welcome the addition of another capable body to our lab staff!