Kevin Righter, NASA-JSC
This newsletter reports 219 new meteorites from the 2012, 2013, 2014 and 2015 ANSMET seasons from Larkman Nunatak (LAR12), Miller Range (MIL13 and MIL15), and Dominion Range (DOM14) areas. Meteorites include ten carbonaceous chondrites (CK, CM, CR, CV) and two EH3 chondrites, as well as 1 diogenite, four eucrites, 3 irons and a pallasite.
Reminder to sign and return your annual inventory
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 Department of Mineral Sciences of the Smithsonian Institution and Astromaterials Curation Office at NASA Johnson Space Center.” 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.
LAR 12310 : LAR 12310 was reclassified as an L6 Chondrite.
ANSMET 2015 – 2016 Field Season
Ralph Harvey, Jim Karner and John Schutt, Case Western Reserve University
For the past several years ANSMET field plans have been modest in scope and cost, if you can say that at all about Antarctic fieldwork. This was intentional, given we were dealing with major changes in the formal support structure of our program and other issues (such as the lingering effects of the October 2013 governmental shutdown on the US Antarctic Program). In an effort to keep things inexpensive and easy to support, we avoided “risky ” and logistically difficult visits to new or remote icefields where poor yields and/or logistical costs might occur. One look at this year‘s plans, however, should convince you that modesty has been cast aside for now.
Target icefields to be visited during the 2016-17 field season. The red triangle shows the approximate location of the Shackleton camp. ANSMET team A will systematically search at the icefields around Mts. Cecily and Raymond (center left), while team B will conduct reconnaissance further south, among the icefields in the headwaters region of the Amundsen Glacier (center bottom). The region is roughly 500 statute miles from McMurdo Station.
Our field season begins with a two-person reconnaissance visit to the Elephant Moraine icefields. We were very active in the region up through the mid-90‘s; but increasing local snow cover (associated with the giant iceberg B-15 blocking the escape of sea ice from the Ross Sea) led us to move on to more southerly targets rather than try to force recoveries. B-15 is now officially gone, local climate appears to be resetting, and so it‘s a good time to re-evaluate dedicated searching at the site.
Following that trip, we‘ll take two teams of four out to a new camp in the Shackleton Glacier region. This camp has been in planning for several years, became operational last year, and will provide logistical support for science throughout more southerly parts of the Transantarctic Mountains. We‘ll use this camp as a flight hub and staging ground for our two field parties, each of which will operate independently. “ Team A ”, led by Jim Karner, will conduct season-long systematic recoveries at the icefields around Mts. Cecily, Raymond and Emily. This is a beautiful site that was first explored in 1985, revisited about a decade later, and in spite of a few tries hasn‘t been successfully visited since (it was a planned second target during seasons at nearby Larkman Nunatak). Team A will stay at these icefields for the entire season, and if weather allows may even finish our recovery efforts at this site (one of the homes of the GRO meteorites).
“ Team B ”, led by Ralph Harvey and John Schutt, will be dedicated to reconnaissance. The team‘s targets are several interesting icefields in the headwaters region of the Amundsen Glacier, only one of which has been previously visited (Mts Wisting and Prestrud, where 26 meteorites were recovered in a few days in 1995). Team B will use a pre-deployment overflight to prioritize targets and establish landing sites, and then visit three of them over the course of about 5 weeks. The main goal for Team B is to get boots on the ground and fully evaluate the meteorite recovery potential of each site. Given that the Shackleton camp is likely to be active for several following seasons, our hope is that one or more of these sites will be found worthy of larger scale recovery efforts later on.
Report from the Smithsonian
Cari Corrigan, Geologist (Dept. of Mineral Sci.)
Things are going well in the Division of Meteorites at the Smithsonian. We are anxiously awaiting our new JEOL FEG electron microprobe, which should be delivered at the beginning of November. This new instrument will be used to classify the Antarctic Meteorites.
One nice bit of news — the recent book on the U.S. Antarctic Meteorites (Righter, Corrigan, McCoy and Harvey, 2015 35 Seasons of U.S. Antarctic Meteorites: A pictorial guide to the collection; AGU Press) has been selected for a Smithsonian National Museum of Natural History Science Achievement Award. Thanks to all of those who contributed!
As a reminder, classification of all ordinary chondrites is now done by Energy Dispersive Spectroscopic (EDS) methods using a Scanning Electron Microscope (SEM). This can include the analysis of several olivine and pyroxene grains to determine the approximate Fayalite and Ferrosilite values of the silicates, grouping them into H, L or LL chondrites. Petrologic types are determined by optical microscopy and are assigned based on the distinctiveness of chondrule boundaries on broken surfaces of a 1-3 g chip. While this technique is suitable for general characterization and delineation of equilibrated ordinary chondrites, those undertaking detailed study of any meteorite classified by optical methods alone should use caution. It is recommended that a polished thin section be requested to accompany any chip and appropriate steps for a more detailed characterization should be undertaken by the user.
Chris Anders, our intern over the past 14 months has moved on, and we thank him for all of his hard work in helping to develop the system we are using for the ordinary chondrite SEM analyses, as well as innumerable other improvements he made around the analytical labs in our department. He will be sorely missed and we wish him well!