This newsletter contains classifications for 597 new meteorites from the 2003 and 2004 ANSMET seasons. They include samples from the Cumulus Hills, Dominion Range, Grosvenor Mountains, LaPaz Icefield, MacAlpine Hills, and the Miller Range. Macroscopic and petrographic descriptions are given for 25 of the new meteorites: 1 acapulcoite/lodranite, 1 howardite, 1 diogenite, 2 eucrites, 1 enstatite chondrite, four L3 and two H3 chondrites, 2 CM, 3 CK and 1 CV chondrites, three R chondrites, and four impact melt breccias (with affinities for H and L). Likely the most interesting sample announced in this newsletter is LAP 04840, with affinity to R chondrites. This meteorite contains approximately 15% hornblende, and has mineral compositional ranges and oxygen isotopic values similar to those of R chondrites. The presence of an apparently hydrous phase in this petrologic grade 6 chondrite is very unusual, and should be of great interest to many meteoriticists.

The Curation website has a new look, and has also been updated and improved:

https://curator.jsc.nasa.gov/

The new website allows one to search the meteorite database by sample number, year, classification, weathering degree, or fracturing degree. There have also been more photos added to the website for certain samples, and additional photos are being added on a regular basis.

The Meteorite Working Group has suggested that we remind the community about samples in the collection that remain ungrouped and unusual. There are several: MAC 87300/301 and LEW 85332 are ungrouped carbonaceous chondrites, QUE 94200 and its pairs (QUE 97289 and QUE 97348 and QUE 99059, QUE 99122, QUE 99157, QUE 99158, QUE 99387) are ungrouped enstatite chondrites, GRO 95551 is a metal-rich ungrouped chondrite, and LEW 88763 and QUE 93148 are ungrouped achondrites.

There are a number of terrestrial samples collected from the Elephant Moraine region of Antarctica. These samples (given the number EET 96400 and 401, Dolerites) have been stored in the large sample cabinet under dry nitrogen at JSC since 1997. Although we would like to remove them from the processing facility, we thought we would ask to see if anyone wishes to study these samples. If you are interested, please get in touch with us as soon as possible. If we don't hear anything by the time of the next newsletter (September 2006), we will remove them from the cabinet.

On December 5, we made the unfortunate discovery that the freezer in the main Meteorite Processing Lab (MPL) room had lost power and was essentially at room temperature inside. The samples within had thawed in their bags. Samples are usually thawed in dry nitrogen to minimize reaction and oxidation. After some investigation into this discovery, we realized that due to construction in Building 31, the power to that freezer had been off since Nov. 11, nearly three weeks. This unfortunate circumstance was dealt with immediately. We moved all samples in the freezer into drying cabinets, and cut the bags to immediately begin the drying process. All 530 samples affected were from the 2003 collection. We have tagged all of these samples in the database as "thawed"; these samples are indicated in the list of meteorites announced in this newsletter. Although most of the samples do not show any effects of being thawed, approximately 1% have more extensive evaporitic growth (sulfates). A full account of the effects on samples will be provided in a future newsletter. The main purpose of this message is to warn those of you who may be interested in doing studies related to low temperature or surface mineralogy.

This newsletter reports classification of almost 600 meteorites and while you might only find a few of these of interest for your research, sorting through all of the equilibrated ordinary chondrites comprises the majority of our work load. In the last 6 months, most of that work was accomplished by long-time Smithsonian meteorite collection manager Linda Welzenbach and Allie Gale. Allie is a name that will be less familiar to you. She has been working for us full-time since graduating from the Univ. of Maryland last summer. She'll be off to graduate school before the next newsletter, but she's helped carry much of the load while I've been off working on Mars (or at least on the Mars rovers).

By late summer, we will have a new collections technician joining us at the Smithsonian in a position to be shared between the meteorite and rock & ore collections. He or she will spend much of his/her time working with Antarctic meteorites, particularly handling all of the samples being transferred to us from JSC. With a little luck, we might even be able to make an introduction to the community in the next newsletter. Stay tuned!

The 2005-2006 ANSMET field season went like clockwork but was a lean one for meteorites - only 171 for the systematic searching team in the Miller Range and 67 for the reconnaissance group exploring several blue ice patches south of the Allan Hills region and west of the Dry Valleys. The problem for the Miller Range group was weather. A wind storm was raging when the team arrived at their new home and it continued for 6 days, narrowly avoiding an ANSMET record. After that it was calm, but then it began to snow, and before long the meteorites were buried, as were the team's hope of finding them. The team stayed busy with detailed reconnaissance and secondary science in support of future seasons; but in the end, only a bit more than a week had been spent systematic searching.

The reconnaissance team also had to deal with strange weather and too much snow, but they got more wind, and moving around let them pick their targets. Unfortunately, they simply didn't have many meteorites to find. This wasn't entirely a surprise- many of the target icefields had been examined by helicopter in the first year of ANSMET and yielded no meteorites at the time. But with modern satellite imagery and search techniques, and a few recent serendipitous finds to guide us, we felt a need for a modern ground-based search of some icefields that had been visited only briefly or not at all. The team examined a lot of promising blue ice, and managed to find a couple of small concentrations, but no major new concentrations were found.

In a nutshell, it was a year marked by odd weather and low recovery numbers. While it certainly wasn't our plan to recover only a fifth of the typical haul of recent years, we worked hard and dealt with the conditions as best we could. I'm sure there are a few rocks in the 05 collection that will interest you. Certainly we're happy to let the curators at JSC and the Smithsonian catch their breath just a bit after several seasons of 1200+ recoveries.

We have started a terrestrial ages survey of Antarctic meteorites, based on the concentration of cosmogenic ³⁶Cl (half-life = 3.01x10⁵ yr) in the metal fraction. After separation of clean metal and chemical separation of Cl at the Space Sciences Laboratory, University of California, Berkeley, the ³⁶Cl concentrations were measured by accelerator mass spectrometry (AMS) at PRIME Lab, Purdue University (mcaffee@physics.purdue.edu). Table 1 shows the first results of ³⁶Cl concentrations and terrestrial ages in 100 Antarctic meteorites. Since the ³⁶Cl saturation values in the metal phase of small to medium-sized meteorites are in a relatively narrow range of 19-25 dpm/kg (2s), the measured ³⁶Cl concentrations yield a direct measure of the terrestrial age (Nishiizumi et al. 1989). The apparent terrestrial age, T(terr), (in kyr) can be calculated using the following equation:

T(terr) = -434 x ln(A/A₀)

where A is the measured ³⁶Cl concentration and A₀ is the average ³⁶Cl saturation value of 22.1±2.8 dpm/kg-metal (2s) (Nishiizumi 1995). For meteorites with ³⁶Cl concentrations >22.1 dpm/kg we only report an upper limit of the terrestrial age, whereas for meteorites with ³⁶Cl concentrations between 19.5 and 22.1 dpm/kg, we report the possible range of terrestrial ages in Table 1. For meteorites with ³⁶Cl concentrations < 19 dpm/kg there is a small possibility that these low values are due to unusually high shielding conditions or a short exposure age, but this can only be verified by measuring additional cosmogenic nuclides.

For more information about the ³⁶Cl results, or the terrestrial ages, please contact Kuni Nishiizumi (kuni@ssl.berkeley.edu) or Kees Welten (kcwelten@berkeley.edu). This work was supported by NSF-OPP and NASA's Cosmochemistry Program.