Kevin Righter, NASA-JSC
This newsletter reports 543 new meteorites from the 2008, 2009, and 2010 ANSMET seasons from the Miller Range (MIL), Dominion Range (DOM), Buckley Island (BUC), LaPaz Icefield (LAP), and Patuxent Range (PAT). The new samples include 46 new carbonaceous chondrites (33 CO, 8 CV, 2 CK, and 3 CM), 2 R chondrites (likely paired with the unusual hornblende-bearing R chondrite LAP 04840), one L3.8 chondrite, 1 EL6 chondrite, and an Enstatite chondrite impact melt. Among the new achondrites are 3 pallasites, 2 ureilites, and 12 HED meteorites. The HED meteorites are welcome additions to the collection and come on the heels of the Dawn Mission arrival at asteroid 4 Vesta — the probable home of many of the HEDs.
The publication of this newsletter completes the classification of the 2008 season meteorites. The 2008 season yielded 11 carbonaceous chondrites, several chondritic impact melts, 5 eucrites and 2 ureilites. Among these samples were a 1.3 kg eucrite (DOM 08001) and two sizable and paired CO3 chondrites — DOM 08004 and DOM 08006 — with a paired mass close to 1 kg.
The meteorite collection received 56 requests for the Spring MWG meeting, and although all of the sample chips have been prepared and sent out, there are a few thin sections that still are being prepared.
HED compendium goes online
In anticipation of the Dawn Mission spacecraft arrival at asteroid 4 Vesta in August 2011, Kevin Righter and Josh Garber (now UC Davis graduate student) initiated an HED (Howardite-Eucrite-Diogenite) meteorite compendium. As part of the compendium we feature some samples that have been in the collection for some time and analyzed more extensively than others. For example the paired howardites EET 87503 and EET 87513 were slabbed and studied extensively. The photos have not been available online, but the compendium summary includes as much information as possible. This compendium cannot summarize all HED samples as there are close to 1000. However, we will try to add sample summaries to the compendium as time and interest allows.
Correction: Reclassification of MacAlpine Hills 02453 (LL6):
MAC 02453 was classified as a CK5 chondrite in AMN 28(1), reported in MetBull 89. New data by J.T. Wasson and A.E. Rubin (UCLA) show that it is actually an ordinary chondrite (LL6). Bulk composition by INAA: Na 6.1, K 0.97, Ca 12.9, Cr 3.50, Mn 2.59, Fe 177, Ni 8.3 (all mg/g); Sc 8.31, Co 450, Zn 50, Ga 5.0, As 1.35, Se 8.0 (all ug/g); Ru 550, Sb 79, La 318, Sm 195, Eu 79, Yb 197, Os 347, Ir 320 (all ng/g). Contains plagioclase > 50 um in size, chromite, troilite and pentlandite. Magnetite is not present, as originally reported. The published mineral compositions, Fa32 and Fs26, and bulk composition are all consistent with an LL classification.
2010-2011 ANSMET Field Season Report
Ralph Harvey, Principal Investigator, ANSMET
For the 2011-2012 field season ANSMET will be returning to the Miller Range Icefields, nestled among and against the western (icesheet) side of the Transantarctic mountains, about half-way between McMurdo and South Pole Stations. Our visits to this location have followed a very typical trajectory from reconnaissance to systematic recovery. First came a helicopter-supported day trip in 1985 that yielded one meteorite and suggested the site had at least some potential; but not enough to raise it above the Lewis Cliff Ice Tongue and other nearby sites on our priority list. It was almost 15 years later (in 1999) that we returned to the Miller Range, sending a two-person team for a 3-day visit that yielded 30 meteorites, most in the first few hours. Getting more serious, in 2003 we sent our newly-minted four-person reconnaissance team to the site. They wandered across the breadth of the Miller Range icefields, recovering over 100 specimens (including a new nakhlite). With ample evidence that a full-scale recovery effort would not be wasted, we've sent an 8-person systematic searching team to the Miller Range every other year, recovering well over 2000 meteorites.
2011-2012 continues that trend, and while some of you might think it has gotten boring, the opposite is true. First, from a geographical perspective it is incredibly diverse, a place where the East Antarctic icesheet deviates from monolithic eastward motion into glaciers of all scales, dodging spectacular metamorphic ridges and granitic domes on the way to the Ross Ice Shelf. This diversity in ice flow is mirrored by the presence of blue ice in a wide variety of settings, and meteorites seem to show up on virtually every scrap of blue ice no matter how improbably located. During the upcoming season, we'll be visiting some of these extremes. We'll start the season at the north end of the Miller Range, exploring some small icefields perched along the edges of the massive Nimrod Glacier. We'll also explore some broad sections of the Ascent and Argosy glaciers where a few meteorites have been found mixed in with terrestrial rocks by the millions. Ahem. We'll spend the remainder of the season conducting the first systematic searches of the massive Southern Miller Range icefields. Truthfully we don't know if we'll bring back a thousand meteorites or a dozen; but there's no doubt we expect to be surprised.
Report from the Smithsonian
Cari Corrigan, Geologist (Dept. of Mineral Sci.)
The Smithsonian Curation Facility
This newsletter announces the classification of 543 meteorites and closes out the classification of the 2008-2009 season (Dominion Range, DOM, '08's). Since the last newsletter, our thin section preparator, Jonathan Cooper, moved to the Geology Department at Carleton College in Minnesota. Thankfully, our contractor, Nicole Lunning (MSc, UC Davis, 2009), has stepped in to keep the process moving along. She has done a fantastic job learning the thin section making process and has produced some very nice sections. A posting for a new thin section preparator/microbeam technician is currently listed on USA Jobs. We have also brought Dr. Andrew Beck on board as a postdoctoral fellow working with Tim McCoy on the Dawn mission. Andrew is a recent graduate of the University of Tennessee and he is interested in the process of meteorite classification.
An important piece of news that affects requests: The new curation facility at our offsite support center, reported in the Spring 2011 newsletter, is still not operational due to delays in its final stages of assembly and the recent earthquake (August 23, 2011). We are still unable to access meteorites currently stored in this facility. While our specific facility fared well during the earthquake, other portions of the Support Center did not, and we expect attention to be focused on those repairs. For those who wish to request meteorites that are stored there, please accept our apologies for the delays to the process; we will do our best to suggest material from other, accessible, meteorites that would be suitable for your project. We expect this facility to be completed and fully operational by the end of 2011, so please bear with us!