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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, E09005, doi:10.1029/2005JE002426, 2005

MIL03346, the most oxidized Martian meteorite: A first look at spectroscopy, petrography, and mineral chemistry

M. Darby Dyar

Department of Astronomy, Mount Holyoke College, South Hadley, Massachusetts, USA


Allan H. Treiman

Lunar and Planetary Institute, Houston, Texas, USA


Carlé M. Pieters

Department of Geological Sciences, Brown University, Providence, Rhode Island, USA


Takahiro Hiroi

Department of Geological Sciences, Brown University, Providence, Rhode Island, USA


Melissa D. Lane

Planetary Science Institute, Tucson, Arizona, USA


Vanessa O'Connor

Department of Geology, Smith College, Northampton, Massachusetts, USA


Abstract

Meteorite MIL03346, recovered from Antarctica, is a nakhlite: an augite clinopyroxenite inferred to have originated from Mars' surface. MIL03346 contains ∼70% augite and 3% olivine in a fine-grained mesostasis of basaltic glass, olivine, titanomagnetite, and pyrrhotite. Part of the olivine is altered to fine-grained ferric clays and oxides: “iddingsite” as described in other nakhlites. Chemical compositions of augite and olivine (FeO/MnO and Fe/Mg) are nearly identical to those of other nakhlites and are consistent with a Martian origin. The augite contains significant Fe3+: ∼24% of total iron by Mössbauer spectroscopy and ∼13% by elemental analyses and crystal chemistry. This proportion of Fe3+ in augite is consistent with high-temperature equilibration near the QFM oxygen buffer. Thermal emission spectra are similar to those of other nakhlites. Visible to mid-IR spectra of MIL03346 show the same absorption features as do other nakhlites but at distinctly lower reflectances (which likely represent Fe3+ in augite and magnetite). MIL03346 appears to contain the most Fe3+ of any Martian meteorite studied to date and to have come from the most oxidizing magmatic environment yet reported.

Received 5 March 2005; accepted 6 June 2005; published 15 September 2005.

Keywords: emission spectroscopy; meteorites; MIL03346; Mössbauer spectroscopy; reflectance spectroscopy; SNC.

Index Terms: 6225 Planetary Sciences: Solar System Objects: Mars; 6240 Planetary Sciences: Solar System Objects: Meteorites and tektites (1028, 3662); 3929 Mineral Physics: NMR, Mossbauer spectroscopy, and other magnetic techniques; 3620 Mineralogy and Petrology: Mineral and crystal chemistry (1042).

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Citation: Dyar, M. D., A. H. Treiman, C. M. Pieters, T. Hiroi, M. D. Lane, and V. O'Connor (2005), MIL03346, the most oxidized Martian meteorite: A first look at spectroscopy, petrography, and mineral chemistry, J. Geophys. Res., 110, E09005, doi:10.1029/2005JE002426.