Determination of Martian meteorite lithologies and mineralogies using vibrational spectroscopy

We have acquired thermal infrared emission spectra of four Martian meteorite samples, ALH77005, Nakhla, Zagami, and EET79001, representing three major lithologies (lherzolite, clinopyroxenite, and basalt). The spectra of these meteorites are significantly different from each other, and we can distinguish the three lithologies easily on the basis of their spectral morphologies. Using a linear deconvolution model, the modal mineralogies of ALH77005, Nakhla, and Zagami were derived from their spectra to within 2-19% of the modes derived by optical methods. For Zagami and EET79001, the correct mineral types were identified as present using the linear method, although an exact spectral match using available end-member spectra was not obtained, probably due to the lack of a pigeonite end-member spectrum or shock effects in the meteorites. The meteorite spectra we have acquired will be used for comparison with data to be returned by the thermal emission spectrometer (TES) on the Mars Global Surveyor orbiter and would also be useful for comparing to future rover- or lander-based thermal IR spectra. Based on our results, comparisons of mineral end-member and meteorite spectra with TES spectra of coarse regolith and rocky regions should aid identification and mapping of Martian surface lithologies and unit mineralogy.