Antarctic meteorites

The meteorite specimens collected by ANSMET and by other investigators include most of the groups of stony, stony-iron, and iron meteorites listed in Table 18.1. 

Hexahediites Kamacite, schreibersite, troilite, daubreelite, graphite 4-6 No 

Octahediites Kamacite, taenite, awaruite, plessite, schreibersite, troilite, cohenite (FejC), graphite (diamond) 6 Yes 

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The desorption laser can be tracked across the surface of the meteorite so the plume of molecules can be associated directly with internal structures and morphology on the meteorite surface. The internal morphology of a meteorite is accessed by cleaving the sample in an ultraclean environment to prevent terrestrial contamination, followed by the laser desorption analysis. Nearly all meteorites have been studied in this way producing a mature field of research, however, the details of just two meteorites will be discussed in some detail. The Murchison and ALH84001 meteorites have provoked considerable interest, particularly the Antarctic meteorite ALH84001, which was the subject of a NASA announcement regarding life on Mars. 

Bogard D. D. and Johnson P. (1983). Martian gases in an Antarctic meteorite, Science, 221 651-654. 

Figure 14 shows the Cl data [13] where the events are plotted on a two-parameter display of range vs. energy. When improved chemical separation preparation techniques were used in later experiments on antarctic meteorites [14], the lower limit of Cl detection that was reached was 2 x 10 16 for 36C1/C1, with a quoted accuracy between 5 percent and 10 percent. 

Fireman, E. L., Carbon-14 Dating of Antarctic Meteorites and Antarctic Ice (Abstract), In Lunar and Planetary Science XI, Lunar and Planetary Institute, Houston, 1980, 288-290. 

Bauer et ah, 1986). It is also a significant corrosion product of Fe alloy phases on Antarctic meteorites where its formation is induced by the chloride ions coming from airborne seaspray and/or volcanic activity (Buchwald and Clarke, 1989). In these meteorites, akaganeite is located adjacent to the corroding surface and beneath a layer of goethite/spinel into which it eventually transforms. 

Buchwald, U.F. Clarke, R.S.Jr. (1989) Corrosion of Fe-Ni alloys by Cl-containing akaga-neite (P-FeOOH) The Antarctic meteorite case. Am. Min. 74 656-667 Buckland, A.D. Rochester, C.H. Topham,... 

Huss, G. R. (2004) Implications of isotopic anomalies and presolar grains for the formation of the solar system. Antarctic Meteorite Research, 17, 132-152. 

Ouri, Y., Shirari, N. and Ebihara, M. (2003) Chemical composition of Yamato (Y)980459 and Y000749 Neutron-induced prompt gamma-ray analysis study. Antarctic Meteorite Research, 16, 80—93. 

Clarke, R. S., Appleman, D. E. Ross, D. R. 1981 An Antarctic meteorite contains preterrestrial impact-produced diamond and lonsdaleite. Nature, Lond. 214, 396-398. 

Antarctic Meteorite Newsletter. Johnson Space Center, Houston, TX, 1988... 

Fig. 4. Profile of the normalized F concentration for the Antarctic Meteorite ALHA79025 by NRA compared to the earlier classical analysis of thin layers (see text). Reproduced with permission from Noll et al. [38],...

Fig. 5. Concentration profiles for three Antarctic meteorites of different exposition duration on the ice sheet (see Table 1 for details). Reproduced with permission from Noll [59],...

Diffusion tends to equilibrate concentration differences between two reservoirs upon contact fluorine concentration profiles develop at the boundary of the two compartments as a function of time. Studies of the distribution of this trace element in archaeological samples such as bones, teeth or flints allow to gain some age information on the excavated objects of a burial site. The presented technique using beams of accelerated protons allows to measure fluorine diffusion profiles with an excellent space resolution. The surface exposure duration was deduced by the same method for Antarctic meteorites. 

K. Noll, M. Dobeli, U. Krahenbuhl, Fluorine profiles in Antarctic meteorites by nuclear reaction analysis, Fresenius J. Anal. Chem. 361 (1998) 713-715. 

Degree of terrestrial weathering is an additional classihcation parameter commonly applied to meteorite hnds. Two classihcation schemes are used one for hand specimens of Antarctic meteorites (commonly used), and one for meteorites as they appear in polished sections (rarely used). Weathering categories for hand specimens are A—minor rustiness B—moderate rustiness C—severe rustiness and e—evaporite minerals visible to the naked eye (e.g., Grossman, 1994). 

Bischoff A. and Metzler K. (1991) Mineralogy and petrography of the anomalous carbonaceous chondrites Yamato-86720, Yamato-82162, and Belgica-7904. Proc. NIPR Symp. Antarct. Meteorit. 4, 226-246. 

Hiroi T., Bell J. F., Takeda H., and Pieters C. M. (1993b) Spectral comparison between olivine-rich asteroids and paUasites. Proc. NIPR Symp. Antarct. Meteorit. 6, 234-245. 

Ikeda Y., Ebihara M., and Prinz M. (1997) Petrology and chemistry of the Miles HE iron I. Description and petrology of twenty new sihcate inclusions. Antarct. Meteorit. Res. 10, 355-372. 

Kimura M., Tsuchiayama A., Fukuoka T., and limura Y. (1992) Antarctic primitive achondrites, Yamato-74025, -75300, and -75305 their mineralogy, thermal history, and the relevance to winonaites. Proc. NIPR Symp. Antarct. Meteorit. 5, 165-190. 

Noguchi T. (1994) Petrology and mineralogy of the CooUdge meteorite (CV4). Proc. 7th NIPR Symp. Antarct. Meteorit. 42-72. 

Paul R. L. and Lipschutz M. E. (1990) Consortium study of labile trace elements in some Antarctic carbonaceous chondrites Antarctic and non-Antarctic meteorite comparisons. Proc. NIPR Symp. Antarct. Meteorit. 3, 80-95. 

Tomeoka K., KojimaH., and YanaiK. (1989) Yamato-86720 a CM carbonaceous chondrite having experienced extensive aqueous alteration and thermal metamorphism. Proc. NIPR Symp. Antarct. Meteorit. 2, 55—74. 

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