Kevin Righter, NASA-JSC
This newsletter announces the availability of 147 new meteorites collected from the 2017-18 and 2018-19 ANSMET seasons. The three GRO17 samples represent the last of the 2017 season samples to be classified, and include an ungrouped achondrite, an ungrouped (low FeO) chondrite, and an EH3 chondrite. Samples from the Dominion Range include a lunar basaltic breccia, an L impact melt and several ordinary chondrites (H3.5, H4, L3.8), including a few with unusual features such as shock melt veins or large chondrules.
In addition to these new samples, we propose reclassification of several samples, as well as pairing reassessment for others. Additionally, field collection information is presented for other samples and now added to our webpages.
Re-classifications and pairing assessments
MIL 091004 was classified as a lodranite in AMN 35, 2. Petrologic, geochemical, and isotopic data acquired since then has necessitated the reclassification of this sample as a ureilite (Day et al., 2017). Pyroxene and olivine compositions from MIL 091004 fall within the compositional space defined by ureilites. In addition, oxygen isotopic composition clearly shows that MIL 091004 is a ureilite, not a lodranite. It is thus well justified to reclassify this sample as a ureilite.
Day, J.M., Corder, C.A., Cartigny, P., Steele, A., Assayag, N., Rumble III, D. and Taylor, L.A., 2017. A carbon-rich region in Miller Range 091004 and implications for ureilite petrogenesis. Geochimica et Cosmochimica Acta, 198, pp.379-395.
LAR LL3.8 chondrites
There are 14 LL3.8 chondrites that were recovered from a small area within the LAR dense collection area. These were announced in earlier newsletters and were not all paired with each other. Inspection of the field map for all these samples indicates they were recovered within 1 km of each other, and likely all paired together. Since they were classified and announced in small batches and over an 8 year period, they were not recognized as pairs until some time had passed. These include LAR from the 06 season 279, 283, 301, 320, 343, 469, 674, 772, 774, and from the 12 season 034, 075, 078, 180 and 203.
EET and QUE Howardite Pairings
EET 87532 reclassified as a howardite.
QUE 97002 reclassified as a howardite.
An initially defined pairing group (e.g., AMN 11, 2) consisting of EET 87503, EET 87509, EET 87510, EET 87512, EET 87518, and EET 87531 has been reevaluated by Mittlefehldt et al. (2013). Based on petrography, mineralogy, petrology, bulk composition, and find locations, EET 87503 was removed from this group and paired with EET 87513, and EET 87512 was removed from this group to be unpaired. The original group also gained EET 92022, EET 83376, EET 87532, EET 99400 and EET 99408.
Five GRO howardites have been reevaluated by Mittlefehldt et al. (2013). Based on petrography, mineralogy, petrology, bulk composition, and find locations, QUE 94200, 97001, 99033 and 99058 are paired together; QUE 97002 remains unpaired.
GRO 95602 was initially paired with four other GRO howardites: GRO 95534, GRO 95535, GRO 95574, and GRO 95581. These five howardites have been reevaluated by Mittlefehldt et al. (2013), Cartwright et al. (2014) and Lunning et al. (2016). Based on petrography, mineralogy, petrology, and bulk composition, GRO 95534, 535, 574, and 581 are paired together; GRO 95602 has been removed from this pairing group and is unpaired.
- Mittlefehldt, D. W., Herrin, J. S., Quinn, J. E., Mertzman, S. A., Cartwright, J. A., Mertzman, K. R., & Peng, Z. X. (2013). Composition and petrology of HED polymict breccias: The regolith of (4) Vesta. Meteoritics & Planetary Science, 48(11), 2105-2134.
- Lunning, N. G., Welten, K. C., McSween Jr, H. Y., Caffee, M. W., & Beck, A. W. (2016). Grosvenor Mountains 95 howardite pairing group: Insights into the surface regolith of asteroid 4 Vesta. Meteoritics & Planetary Science, 51(1), 167-194.
- Cartwright, J. A., Ott, U., & Mittlefehldt, D. W. (2014). The quest for regolithic howardites. Part 2: Surface origins highlighted by noble gases. Geochimica et Cosmochimica Acta, 140, 488-508.
MET, GRO and LEW Low Grade Ordinary Chondrites
MET 00621 was added to the MET 00452/00526 pairing group as discussed in Righter et. al. (2021).
Righter et al. (2021) also proposed the following changes:
- MET 00489, MET 01211 and MET 01322 are all paired and type L3.6. MET 00621 was removed from this pairing group and instead paired with MET 00452 and MET 00526.
- MET 96503, MET 96515, MET 01051, MET 01056, and MET 01057 are all paired and type L3.10.
- MET 00506, MET 00552, and MET 00607 are all paired and type H3.10.
- GRO 03015 and GRO 03061 are paired and both type L3.10.
- GRO 95502, GRO 95504, GRO 95505, GRO 95512, GRO 95539, GRO 95542, GRO 95544, GRO 95545, GRO 95546, and GRO 95550 are all paired and type L3.2.
- LEW 85434, LEW 85437, LEW 87248, LEW 87284, LEW 88254, and LEW 88462 are all paired and type L3.15.
- LEW 86018, LEW 86102, LEW 86144, LEW 86158, LEW 86207, LEW 86270, LEW 88520, and LEW 88634 are all paired and type L3.2.
- LEW 85401, LEW 86127, and LEW 88033 are all paired type L3.3.
- LEW 85339, 86246, 86367, 86505, 88175, 88261, 88452, 86105, and 86213 are all paired type L3.4.
- LEW 88263 was listed incorrectly as a L3.7 in Righter et al. (2021). This sample should also be paired with the LEW 85339 L3.4 group.
- LEW 86408, LEW 86417, LEW 86436, LEW 86495, LEW 88286, LEW 88617, LEW 88632, and LEW 88644 are all paired type L3.5.
- LEW 88632 was mistakenly listed as L3.5 in Righter et al. (2021) - it is L3.6 and should thus be paired with LEW 85396.
- LEW 85396, LEW 85452, LEW 86347, LEW 88146 are all paired type L3.6.
- LEW 88328, LEW 88594, LEW 88621, LEW 88696, LEW 93891 are paired and Type L3.7.
- LEW 88467 and LEW 87093 are paired and type L3.8.
- Righter, K., Schutt, J., Lunning, N., Harvey, R., & Karner, J. (2021) Identification and pairing reassessment of unequilibrated ordinary chondrites from four Antarctic dense collection areas. Meteoritics & Planetary Science 56, 1556-1578.
Allan Hills CM Chondrites
47 CM chondrites have been recovered from the Allan Hills dense collection area, which spans nearly 70 km x 30 km. The area is comprised of four different subfields: main, near western, middle western, and far western icefields. Pairing within these areas has been addressed in the past (e.g., Benoit et al., 2000), but not reassessed in the last 20-25 years. In these intervening years, a wide variety of analytical results have been acquired and published including noble gas data (Herpers et al., 1990; Krietsch et al., 2021), bulk and isotopic H, C, and N measurements (Alexander et al., 2012; 2013), and spectroscopic data (Hiroi et al., 2021). In addition, the recovery and naming of these samples has varied from season to season which has made the history somewhat confusing so we will try to clarify that here.
Current sample pairings:
Main Icefield: ALH 77306, ALH 78261, ALH 81002, ALH 81312 (none paired with each other)
Near Western Icefield: ALH 84054, ALH 84033 (all paired with ALH 81002)
Middle Western Icefield: ALH 81004, ALH 83016, ALH 84191 (all paired with ALH 81002)
Far Western Icefield:
- ALH 77306, ALH 78261, ALH 81002, ALH 81312 (none paired with each other)
- ALH 83102; 20 pieces were recovered and assigned the same number; described in AMN 8, no. 1 (Feb. 1985) and AMN 9, no. 2 (June 1986), Table 8, page 13.
Other samples recovered from this area include:
- ALH 83100 pairs: ALH 99500.
- ALH 83102 pairs: ALH 83106, ALH 84029, ALH 84030, ALH 84031, ALH 84032, ALH 84034, ALH 84035, ALH 84040, ALH 84041, ALH 84042, ALH 84043, ALH 84044, ALH 84045, ALH 84047, ALH 84048, ALH 84049, ALH 84051, ALH 85004.
- ALH 85005 and pairs ALH 85007, ALH 85008, ALH 85009, ALH 85010, ALH 85011, ALH 85012, ALH 85013
- ALH 81002 pairs: ALH 82100, ALH 82131, ALH 84036, ALH 84039, ALH 84046, ALH 84050, ALH 84053
- ALH 85106
- ALH 90407
The following observations have been made that allow us to reconsider the pairing among the Allan Hills CM chondrites.
- The ALH 81002 pairing group is spread over a very large distance, close to 70 km. This seems too large given knowledge of showers and strewnfield sizes and mass recovered (e.g., Righter et al., (2021)). We thus suggest unpairing the samples from the far and middle western groups dividing this group into three: ALH 81002 from the main icefield (and 2 pairs in near western field, ALH 84033 and ALH 84054), ALH 81004 middle western icefield (and 2 pairs ALH 83016 and ALH 84191), and ALH 82100 far western icefield (and ALH82131, ALH 84036, ALH 84039, ALH 84046, ALH 84050, and ALH 84053, as well as two additional samples discussed in (F) and (G)).
- Pieces of ALH 83100 and ALH 83102 and their respective paired samples have a similar appearance in hand specimens with a blocky fracture, sometimes with conchoidal fracture surfaces. This distinctive appearance is supported by (C), (D), and (E) below.
- Krietsch et al. (2021) show that the ALH fields have at least three groups of different ages: ALH 84042 (0.3 Ma), ALH 84033 (6.1 Ma), and ALH 85013 (19.8 Ma). The youngest age corresponds to the same age as obtained for ALH 84042 by Herpers et al. (1990). The 6.1 Ma age for ALH 84033 is also in agreement with the previous work of Herpers et al. (1990). These results also suggest that ALH 84042, 84044, 84029, 83102, and 83100 all have the same young age ~0.2 Ma.
- The ALH 83100 and ALH 83102 groups have the same CRE age, as well as the same H,C,N content as measured by Alexander et al. (2012, 2013), while also distinct from that of the ALH 81002 and ALH 85005 (85013) groups.
- Finally, the reclassification of the samples paired with ALH 83100 (83102 and pairs), from CM2 to CM1/2 is consistent with the original reclassification of ALH 83100 by Zolensky et al. (1997) and subsequent spectroscopic work on the paired pieces by Hiroi et al. (2021) supportive of their more hydrated or aqueously altered than typical CM2.
- ALH 99500 seems not like ALH 83100, in appearance, but was paired with it anyway. It looks like it should instead be paired with the ALH 82100 pairing group in that area (see discussion in (A) above).
- ALH 90407 looks like it could be crumbly in photos which would put it with ALH 82100 group (see discussion in (A) above).
- ALH 85106 looks blocky which would put it with ALH 83100.
Therefore, here are the newly adjusted pairing groups suggested by all this new work, hand sample observations, and find locations:
Main Icefield: ALH 77306, ALH 78261, ALH 81002, ALH 81312 (no changes)
Near Western Icefield: ALH 84054, ALH 84033 (both paired with ALH 81002) (no changes)
Middle Western Icefield: ALH 81004 (paired with ALH 83016, ALH 84191)
Far Western Icefield:
- ALH 83100 (paired with ALH 83102, ALH 83106, ALH 84029, ALH 84030, ALH 84031, ALH 84032, ALH 84034, ALH 84035, ALH 84040, ALH 84041, ALH 84042, ALH 84043, ALH 84044, ALH 84045, ALH 84047, ALH 84048, ALH 84049, ALH 84051, ALH 85004, ALH 85106).
- ALH 85005 (paired with ALH 85007, ALH 85008, ALH 85009, ALH 85010, ALH 85011, ALH 85012, ALH 85013).
- ALH 82100 (paired with ALH 82131, ALH 84036, ALH 84039, ALH 84046, ALH 84050, ALH 84053, ALH 90407, and ALH 99500).
Future work could examine the CRE ages of the Main icefield samples, as well as the Middle Western (ALH 81004) and Far Western (ALH 82100) pairing groups.
- Krietsch, D., Busemann, H., Riebe, M. E., King, A. J., Alexander, C. M. D., & Maden, C. (2021) Noble gases in CM carbonaceous chondrites: Effect of parent body aqueous and thermal alteration and cosmic ray exposure ages. Geochimica et Cosmochimica Acta 310, 240-280.
- Herpers, U., Vogt, S., Signer, P., Wieler, R., Beer, J., & Wölfli, W. (1990) Cosmogenic radionuclides and noble gases in Allan Hills C-chondrites. In Differences Between Antarctic and Non-Antarctic Meteorites (pp. 46-48).
- Hiroi, T., Kaiden, H., Imae, N., Misawa, K., Kojima, H., Sasakia, S., Matsuokaa, M., Nakamura, T., Bish, D.L., Ohtsuka, K., Howard, K.T., Robertson, K.R., and Milliken, R.E. (2021) UV-visible-infrared spectral survey of Antarctic carbonaceous chondrite chips. Polar Science 29, 100723.
- Alexander C.M.O'D., Bowden,. R., Fogel, M. L., Howard, K. T., Herd, C. D. K., Nittler, L. R. (2012) The provenances of asteroids, and their contributions to the volatile inventories of the terrestrial planets. Science 337, 721-723.
- Alexander C.M.O'D., Howard, K. T., Bowden, R., Fogel, M. L. (2013) The classification of CM and CR chondrites using bulk H, C and N abundances and isotopic compositions. Geochimica et Cosmochimica Acta 123, 244-260.
Samples Recovered in Multiple Pieces:
The following samples from early years of the ANSMET program were recovered in multiple pieces and given the same generic sample number (group 1 below), or two generic numbers were combined and renumbered (group 2 below). We have added notes to their webpage descriptions indicating this unique history
1) multiple pieces given the same generic:
EET 90051 (2), EET 90053 (15), EET 90610 (19), EET 90698 (2), EET 90700 (2), EET 90364 (2)
2) two generic numbers were combined and renumbered
LEW 87016 (combined with LEW 87024), EET 87520 (combined with EET 87524), EET 79007 (combined with EET 79008), and EET 79009 (combined with EET 79012).
Report from the Smithsonian
Cari Corrigan, Research Geologist (Dept. of Mineral Sciences)
After a tumultuous two years, the Smithsonian fully reopened to staff in May of this year. This newsletter announces the classification of 150 new meteorites, possibly a smaller number than our previous pace, but classifications were able to be conducted in the usual collaborative manner, using both electron microprobe and EDS analyses for this newsletter, as well as allowing us to work together in person to review data and describe meteorites.
On a personnel note, we welcomed Kelsey Falquero, a Collections Technician at the NMNH, to our Division of Meteorites team back in the spring on a temporary assignment. Kelsey has been working with us in both the Antarctic and main meteorite collections, and we are excited to announce that she has been permanently reassigned to the Department of Mineral Sciences and will continue working with us, and all of you.
The new scanning electron microscope ordered by our department last year has been delivered, installed, and optimized. Training for the laboratory staff is currently taking place on this new instrument, which will eventually be used to classify ordinary chondrites using the dual EDS system.
Our collections have reopened, and we are diligently moving through the backlog of requests we have received since early 2020. We appreciate your patience as we get back to a more normal way of working.
Jim Karner, University of Utah
Ugggh, we've been cancelled again! Last May, ANSMET learned that our highly anticipated return to the field in 2022-23 is not going to happen. There are just too many science projects waiting to get back into the field, and too few logistical resources available to support them all. While we are disappointed, we understand the reasons for the cancellation, and we are stoked for a return to the field in 2023-24.
In the meantime, we will plan for the final return to the Davis Nunataks - Mt. Ward (DW) icefields, at the top of the Beardmore Glacier. ANSMET has recovered over 3000 meteorites from DW, and we really hope we can finish up the area in a couple of week's worth of work - mainly snowmobile sweeps (Figure 4) and walking a couple of unsearched moraines. If we do finish up at DW in a timely fashion, we'd then make a camp move to the nearby Dominion Range Main Icefield (DOM) and resume efforts there (last ANSMET visit in 2003). These are our preferred field plans - hopefully we'll be in the field in December of '23 to execute them!