Comparative Raman microscopy of a Martian meteorite and Antarctic lithic analogues

The Raman microspectra of the Nakhla SNC meteorite, which probably originat es from Mars, are reported here for the first time. The specimen is shown t o be heterogeneous, even at a sampling level of 2 mu m, but several importa nt mineralogical features have been identified, including clinopyroxene, ol ivine and plagioclase. In some sampling regions, rs-quartz particles are ev ident 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 a nalyses were made on epilithic examples of Xanthoria elegans from Crater Ci rque, northern Victoria Land, Antarctica, and cryptoendoliths from East Bea con, McMurdo Dry Valleys, as positive controls for microbial organics in co ld, arid habitats analogous to former Martian conditions. Finally, an asses sment is made of the potential role of Raman spectroscopy for extra-terrest rial characterisation of geological specimens. (C) 1999 Elsevier Science Lt d. All rights reserved.