SEM STUDIES OF ANTARCTIC LUNAR AND SNC METEORITES WITH IMPLICATIONS FOR MARTIAN NANOFOSSILS: A PROGRESS REPORT. Anne

Several meteorites recovered from Antarctica are believed to have a martian origin. This is evidenced by their ages, chemical compositions, morphologies and trapped gases [1-3]. McKay et al. recently reported finding evidence of possible past life in one of the martian meteorites citing mineralogy, morphological phases, PAHs, and microfossils [4]. However, alternate explanations of the origin of the microfossils include them being laboratory artifacts or Antarctic contamination, since bacteria are known to survive in very harsh conditions including Antarctica. The purpose of this project is to examine these alternate explanations by studying several Antarctic lunar and SNC meteorites. If forms are found in lunar meteorites that are similar or identical to those found in martian meteorites, then it will be hard to rule out the idea that the forms are artifacts or contamination. The moon is an extremely harsh environment, incapable of supporting life. The surface temperature increases approximately 260K from just before lunar dawn to lunar noon. The subsurface temperatures vary greatly from that, being about 45K higher. The moon’s atmosphere is about 14 orders of magnitude less than the Earth’s. Because of this, the moon is bombarded with radiation: solar wind, galactic cosmic rays, and solar cosmic rays [5]. Notwithstanding a recent announcement of possible ice deposits near the pole [6], the lunar surface is exceptionally dry. Thus, no type of life forms should be present in lunar meteorites. Eight chips of lunar meteorites and three chips of martian meteorites are being studied (table 1): Table 1 Samples studied Meteorite Description [7][8] ALH 81005* Anorthositic regolith brecciaHighland EET 87521 Basaltic breccia-Mare MAC 88104** Anorthositic regolith brecciaHighland MAC 88105** Anorthositic regolith brecciaHighland QUE 93069* Anorthositic breccia QUE 94281 Basalt-rich breccia EET 79001 Basaltic shergottite ALH 77005 Lherzolitic shergottite ALH 84001 Coarse-grained orthopyroxenite *two chips were studied **paired meteorites