Comparative micro-Raman study of the Nakhla and Vaca Muerta meteorites

A comprehensive micro-Raman spectroscopic analysis of the Nakhla and Vaca Muerta meteorites is reported. The major and minor mineral components were identified from comparison with mineralogical standards and literature databases. The compositions of pyroxenes and olivines were obtained using only this technique and correlation data between band parameters and the chemical composition of reference materials existing in the literature. The presence of calcite in both meteorite specimens was noted; its identification inside eucrite grains in the Vaca Muerta meteorite is particularly noteworthy. Their spectral parameters show strong similarities. Aragonite associated with calcite is reported for the first time in Vaca Muerta meteorite. Spectra of siderite, which appears associated with clinopyroxenes, are also reported in Nakhla meteorite. Iron oxides were analysed in detail in both meteorites. Magnetite is the main oxide phase observed in Nakhla and goethite, lepidocrocite and magnetite in Vaca Muerta. In both cases haematite was not observed. A comparison of the spectral parameters of these mineral phases observed in both meteorites was made and their possible origin as secondary minerals is discussed. This study stresses the potential of Raman spectroscopy in the mineralogical characterization of meteorites on a very small scale and also the potential applications of Raman spectroscopy for use on landers or rovers on the surface of Mars or other planetary bodies. Copyright  2004 John Wiley & Sons, Ltd.