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Research
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Lawrence Livermore National Laboratory
September, 2001
Dr. K. Nishiizumi and M. W. Caffee, Space Sciences Laboratory.
Results: A document produced for the 64th annual Meteoritical Society Meeting document number 5411 briefly described the following:
NWA 482: the AL26 activity in the exterior sample of NWA 482 is up to 40% higher than that of the interior sample. This excess AL26 is produced by SCR during it 4PI exposure to cosmic rays. The pre-atmospheric radius is estimated at 5.5-7 cm based on a recovered mass of 1015 g and 1-1.5 cm of ablation. The BE10 exposure age is 0.9+/- 0.2 Myr. The saturation values of SCR produced AL26 are 10-25 dpm for the interior sample (1 cm from the crust) and 20-40 dpm for the exterior sample respectively. The latter value is similar to the SCR production rate of AL26 at a depth of ~1.5-2 cm in an object having a radius of 6-7 cm. The CI36 terrestrial age is 60-120 kyr.
University of California Los Angeles
September, 2001
Dr. Paul H. Warren and Dr. Gregory W. Kallemeyn, Institute of Geophysics.
Results:A document produced for the 64th annual Meteoritical Society Meeting document number 5453 briefly described the following:
Cosmic ray exposure evidence confirms NWA 482 is not paired (even in the source-crater/launch sense) with any other lunar meteorite. It has a density of ~2.54 g/cm3 and a porosity of roughly 13%. It is defined as being KREEP-poor which indicates it came from an area of the moon not previously sampled by the Apollo or Luna missions. Everything else in the report reaffirmed what is already known.
The Meteoritical Bulletin
May 31st, 2001
Dr. Jeffrey Grossman, of the Nomenclature Committee, analyzed data provided by the universities.
Results: A permanent serial number and publication were assigned. Please see official bulletin below:
The Meteoritical Bulletin, No. 85
Northwest Africa 482
Lunar meteorite (impact melt breccia)
A 1015 g stone was purchased on 2001 January 9 in Alnif, Morocco, by Michael Farmer. The exact location of find is unknown but it is possibly in Algeria. The stone is complete, oriented, and appears relatively unweathered. Classification and mineralogy (A. Rubin and P. Warren, UCLA, and D. Kring and I. Daubar, UAz): texture is typical of a crystalline impact melt breccia (polymict) with highland affinities; glassy and vesicular melt veins and melt pockets indicate shock subsequent to compaction by an impact event; plagioclase, An95.7Ab4.09Or0.17 (n = 136, UAz); olivine, Fo65-68 (average Fo66) with FeO/MnO = 88 ± 7 g/g (UCLA); olivine Fo68.4 with FeO/MnO = 93.9 ± 7.7 g/g (range: 78.7 to 111) (n = 51, UAz); pyroxene, Fs25Wo17 with nearly uniform Mg/(Mg+Fe) = 67 – 68 mol% and FeO/MnO = 51 ± 6 g/g (n = 10, UCLA); pyroxene, Wo10.3- 51En32.6-63.9Fs42.6-14.2, mean Mg/(Mg+Fe) = 68 mol%, FeO/MnO = 52 ± 8 g/g (n = 28, UAz); glassy melt veins occur in both UCLA and UAz samples; a 0.1 mm vein (UCLA) has SiO2 = 44.3 wt.%, Na2O = 0.3 wt.%, Al2O3 = 30.0 wt.%, FeO = 3.6 wr.%, MgO = 3.9 wt.%, CaO = 17.3 wt.%, and TiO2 = 0.3 wt.%, which may approximate the bulk meteorite composition. Specimens: 312 g main mass with the Hupé brothers, type specimens, 24 g, UCLA, and 18 g, UAz.
University of Washington - Report on Lunar Meteorite NWA 482
March 24th, 2001 - by Dr. Anthony J. Irving and Dr. Scott Kuehner
History: Sample NWA 482 was a 1015 g stone with complete fusion crust recovered in Northwest Africa in late 2000.
Samples Studied: Four part slices and one complete slice provided by Adam and Greg Hupé, who also own the main mass from one end of the meteorite.
Methods: The slices were polished on one side, carbon coated and analyzed by electron microprobe energy-dispersive X-ray analysis. Back-scattered electron images were obtained of each entire slice and of other areas of interest.
Results: This sample contains sparse white clasts of anorthosite in a dominant matrix composed of a complex intergrowth of anorthite, pigeonite, olivine, augite, troilite, Fe-Ni metal, Ti-rich chromite, ilmenite and rare whitlockite and a Zr-bearing titanate mineral. These two lithologies have been subsequently brecciated and injected by veinlets of glass, and the entire sample is coated by a thin glassy fusion crust. The dominant portion of the sample is interpreted as a crystallized impact melt derived from a pre-existing anorthositic lithology composed mainly of anorthite with subordinate ferromagnesian silicates. Metal and troilite in this portion commonly occur as small spherical grains, suggesting that they had been molten, and the silicates are intergrown in a variable, "eutectoid" texture. No grains of zircon were found in the sample despite a diligent search.
Interpretation: NWA 482 is a very fresh sample of ferroan anorthosite from the ancient lunar highlands crust. By analogy with Apollo 16 samples such as 60025, parts of this sample are probably 4.4 to 4.5 billion years old. The original rock has been extensively remelted, presumably by a large impact on the lunar crust more than 4 billion years ago. The extent to which any of the impacting bolide was admixed with the original rock is unknown. At a much later time (probably several tens to hundreds of millions of years ago), the sample was ejected from the Moon by another impact that caused brecciation and injection of melt veinlets which rapidly cooled to glass. After extensive travel in space, the stone fell in Northwest Africa very recently, probably within the last thousand years judging from the freshness of the fusion crust.
Reference: Papike, J.J., Ryder, G. and Shearer, C.K. (1998) Lunar samples. In Planetary Materials, editied by J.J. Papike, Reviews of Mineralogy, vol. 36, pp. 5-1 to 5-234. Mineralogical Society of America, Washington, D.C.
Lunar and Planetary Laboratory – University of Arizona
February 13th, 2001
Dr. David A. Kring performed extensive microprobe analysis.
Results: Recommended sample to be classified as a lunar impact melt (polymict, crystalline) breccia.
The Meteoritical Bulletin
February 10th, 2001
Dr. Jeffrey Grossman, of the Nomenclature Committee, analyzed data provided by the universities and Mike Farmer.
Results: Serial number NWA 482 and official weight of 1015 grams was assigned to the meteorite.
University of Chicago
February 3rd, 2001
Dr. Robert Clayton to perform oxygen isotope analysis.
Results: Pending
University of California Los Angeles
February 2nd, 2001
Dr. Alan Rubin studied material under a Scanning Electron Microscope with microprobe analyzer.
Results: The rock was described as a lunar impact melt. Its plagioclase is An96-97. It has shock veins. The pyroxene is pigeonite with an mg-number of about 70; the olivine is about Fo66. Material was then forwarded to Dr. Robert Clayton of the University of Chicago for oxygen isotope analysis.
Lunar and Planetary Laboratory – University of Arizona
February 1st, 2001
Dr. David A. Kring performed a thin section petrologic study.
Results: It is clearly anorthositic, with pyroxene scattered through it. So, petrographically, it appears lunar.
University of California Los Angeles and the Lunar and Planetary Laboratory – University of Arizona
January 23rd 2001
Universities were both provided samples and agreed to publish results in cooperation.
Results: They determined a lunar origin for this material.
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