Comparative Raman microscopy of a Martian meteorite and Antarctic lithic analogues

The Raman microspectra of the Nakhla SNC meteorite, which probably originates from Mars, are reported here for the first time. The specimen is shown to be heterogeneous, even at a sampling level of 2 mu m, but several important mineralogical features have been identified, including clinopyroxene, olivine and plagioclase. In some sampling regions, rs-quartz particles are evident and in one sample region the nu(CO32-) mode of calcite at 1086 cm(-1) is found. There is no evidence lbr organic chemical content detectable In this meteorite specimen, based on an absence of nu(CH) and delta(CH2) modes near 3000 and 1400 cm(-1), respectively. Comparative Raman spectroscopic analyses were made on epilithic examples of Xanthoria elegans from Crater Cirque, northern Victoria Land, Antarctica, and cryptoendoliths from East Beacon, McMurdo Dry Valleys, as positive controls for microbial organics in cold, arid habitats analogous to former Martian conditions. Finally, an assessment is made of the potential role of Raman spectroscopy for extra-terrestrial characterisation of geological specimens. (C) 1999 Elsevier Science Ltd. All rights reserved.