Program News

Curator's Comments
Kevin Righter, NASA-JSC

This newsletter reports 315 new meteorites from the 2006 and 2007 ANSMET seasons from D’Angelo Bluff (DNG), Scott Glacier (SCO), Graves Nunataks (GRA), Larkman Nunatak (LAR), and Miller Range (MIL).  These new samples include an olivine diogenite and 5 other HEDs, an aubrite, a lunar basaltic breccia, a ureilite, 4 irons, a diversity of carbonaceous chondrites (CV, CO, CM), and L and LL chondrite impact melts. 

Six samples from this field season were collected asceptically by M. Fries, as part of a project to assess microbiological contamination, approved in advance by the Meteorite Working Group between 2005 and 2007.  The samples are MIL 07704, MIL 07705, MIL 07706, MIL 07707, MIL 07708, and MIL 07709.   The collection procedure involved personnel wearing protective clothing (cleanroom overalls, mask, sterile gloves, and booties).  Sterile tongs were used to collect the samples which were placed in sterile aluminum cans, the cans were placed in aluminum foil bags and then in regular ANSMET outer bags.  The main mass of each of these six specially collected samples were placed in a clean aluminum container with silica glass witness plates, and packaged and transported to JSC using the normal protocol.  Other materials are also available, such as examples of the protective clothing used to collect the samples, procedural (and unopened) blanks, and skidoo exhaust. Anyone interested in requesting these samples should contact the JSC Antarctic Meteorite Lab group for additional information and details.

Otway Pairing Group and Strewnfield

We would like to bring to the attention of those who may be interested, a group of samples from near the Otway Massif in the Grosvenor Mountains region. The 03-04 ANSMET Team collected 84 fragments of a ~1.6-km long strewnfield from a blue ice area at the Otway Massif. The strewnfield is not on a relatively level ice surface but is draped over topography with a relief of 12 meters, so it is probably not an example of wind dispersion after a break up once the object resides on the ice surface (the large size of many of the fragments don’t lend themselves to wind transport). These meteorites are paired with GRO 03001 and not extensively fusion crusted. Initial announcements of these samples in the Antarctic Meteorite Newsletter volumes 28 and 29 did not acknowledge or mention that they are part of a pairing group, but notes by the field team indicate that it is a large group, and that there are very few meteorites from this small area that are NOT part of the L5 pairing group. Based on the high degree of weathering of these samples, it is possible this is an old strewnfield, but a better understanding of this issue awaits terrestrial age studies. For more information about this field, see Kress et al. (2007) MAPS 42, #5270. If you are interested in the samples, please contact us about types and availability; some of the samples may be listed as LL5 or H5 in our main database and we can direct you to the most updated information about all the members of this strewnfield.

PNRA Allan Hills Meteorites Available at the Smithsonian Institution

During the 2005-2006 meteorite collection field season of the Italian Programma Nazionale delle Ricerche in Antartide (PNRA), 12 meteorites were recovered from the Allan Hills region. The entire collection of PNRA Antarctic meteorites is curated at the Museo Nazionale dell’Antartide, in Siena, Italy. The Allan Hills 06001 – 06012 meteorites published in The Meteoritical Bulletin No. 92 (see Table 4 therein) were recovered by a PNRA team during a test for geophysical instrumentations for the search for meteorites under snow cover. The selected test area was preliminarily discussed with Dr. R. Harvey and Mr. J. Schutt of the ANSMET program. In recognition of such collaborative efforts for the search for meteorites in Antarctica, representative samples of the above collection have been transferred to the Smithsonian Institution. These samples are all H5 chondrites, and are described in Meteoritical Bulletin 92 [in Meteoritics and Planetary Science 42, 1647-1694, 2007]. They are also linked to the MetBull database at:

http://tin.er.usgs.gov/meteor/metbull.php

Inquiries about access to these samples should be directed to the Smithsonian Institution meteorite group.

GRA06128 and 06129 Update

The paired ungrouped achondrites announced in our August 2007 newsletter, GRA 06128 and GRA 06129, have been studied in some detail now, and we would like to present a brief update on what has been found, based on studies reported at the 2008 LPSC and MetSoc meetings. As a reminder, this unusual meteorite contains nearly 75% sodic plagioclase feldspar, along with significant amounts of olivine and pyroxene in a metamorphic equilibrated texture. The oxygen isotopic values reported in our newsletter were overlapping with the terrestrial fractionation line, making the initial classification a challenge since they did not look like pieces of the Moon or enstatite meteorites. Several groups have now measured oxygen on acid and ethanolamine thioglycollate leached portions of the meteorite and found the oxygen to be slightly lower than the terrestrial fractionation line, and overlapping with the brachinite line (original analyses were affected by terrestrial weathering). Radiogenic isotope studies have shown it to be very old – ~4.54 Ga, and perhaps as old as brachinites. However, noble gas studies have shown that the GRA samples contain smaller excesses of 129Xe and no trapped argon relative to brachinites. Petrologic and geochemical studies suggest it is possibly related to brachinites and chondrites by partial melting processes. Our understanding of these meteorites is not yet complete, and the details of these relationships will need to be worked out. Nonetheless, these initial results help to narrow down the possible source body of these meteorites to the asteroid belt. For more information about published results check out abstracts on the program pages for the 39th LPSC and the 71st Meteoritical Society meetings:

Preview of the 2008-2009 ANSMET field season
Ralph Harvey, ANSMET

Late summer is always hectic for the ANSMET program. This is the time of year when I discover just how poorly our first-order plans are going to fit into the support available from the US Antarctic Program. 20+ years of experience with the program has taught me to be flexible. I carefully read the science-support tea leaves, hoping for no surprises and ready to make adjustments to our schedule, available flight hours, whatever it takes to get us out into the field and recovering meteorites. Just as the students return to campus, the tension is reaching a peak, with field party members worrying about passing their physicals, and roadblocks to ANSMET’s schedule either coming down or diverting us in a new direction.

This summer those roadblocks have forced us onto a detour. Immediately after last season we began to see signs of shortfalls in aircraft availability, and with this in mind we planned to send a team of reduced size (6 people instead of 8) to the LaPaz icefields. In the end, even that downsizing wasn’t enough; in mid-July we were told that aircraft shortages required retargeting our efforts toward an icefield closer to McMurdo. Plan B is therefore now in effect. We hope to deploy to the icefields between Mount Ward and the Davis Nunataks in early December, and traverse to the Dominion Range icefield if time allows. These icefields lie at the head of the Beardmore Glacier, and are the home of the DOM meteorites. 152 specimens were recovered from these icefields during reconnaissance visits in 1985 and 2003. The 08-09 expedition will be the first to conduct systematic searching in the region.

We expect this to be a challenging season, not only because logistical support is strained, but because there are a lot of terrestrial rock on the target icefields, notably the dark and glassy Kirkpatrick basalt. However, the Dominion Range area is also astoundingly beautiful and this year in particular promises some interesting historical resonance. It was in late December of 1908 that Ernest Shackleton pioneered his route up the Beardmore Glacier and on the 100th anniversary of that moment, we’ll be within a few miles of where he and his colleagues (Wild, Marshall and Adams) became the first to stand on the East Antarctic Polar Plateau. Here’s hoping the season brings us some of Shackleton’s hardiness, wisdom, flexibility, and a few never-before-seen goodies of our own.