SPECTROSCOPIC ANALYSIS OF MARTIAN METEORITE ALLAN-HILLS-84001 POWDER AND APPLICATIONS FOR SPECTRAL IDENTIFICATION OF MINERALS AND OTHER SOIL COMPONENTS ON MARS

Spectroscopic measurement and analysis of Martian meteorites provide i mportant information about the mineralogy of Mars, as well as necessar y ground-truths for deconvolving remote sensing spectra of the Martian surface rocks. The spectroscopic properties of particulate ALH 84001 from 0.3 to 25 mu m correctly identify low-Ca pyroxene as the dominant mineralogy. Absorption bands due to electronic transitions of ferrous iron are observed at 0.94 and 1.97 mu m that are typical for low-Ca p yroxene. A strong, broad water band is observed near 3 mu m that is ch aracteristic of the water band typically associated with pyroxenes. We aker features near 4.8, 5.2 and 6.2 mu m are characteristic of particu late low-Ca pyroxene and can be distinguished readily from the feature s due to high-Ca pyroxene and other silicate minerals. The reflectance minimum occurs near 8.6 mu m for the ALH 84001 powder, which is more consistent with high-Ca pyroxene and augite than low-Ca pyroxene. The dominant mid-infrared (IR) spectral features for the ALH 84001 powder are observed near 9 and 19.5 mu m; however, there are multiple feature s in this region. These mid-IR features are generally characteristic o f low-Ca pyroxene but cannot be explained by low-Ca pyroxene alone. Sp ectral features from 2.5-5 mu m are typically associated, with water, organics and carbonates and have been studied in spectra of the ALH 84 001, split 92 powder and ALH 84001, splits 92 and 271 chip surfaces. W eak features have been identified near 3.5 and 4 mu m that are assigne d to organic material and carbonates. Another feature is observed at 4 .27 mu m in many surface spots and in the powder but has not yet been uniquely identified. Spectroscopic identification of minor organic and carbonate components in this probable piece of Mars suggests that det ection of small amounts of organics and carbonates in the Martian surf ace regolith would also be possible using visible-infrared hyperspectr al analyses. Laboratory spectroscopic analysis of Martian meteorites p rovides a unique opportunity to identify the spectral features of mine rals and other components while they are embedded in their natural med ium.