SEARCH FOR PAST LIFE ON MARS - POSSIBLE RELIC BIOGENIC ACTIVITY IN MARTIAN METEORITE ALH84001

Fresh fracture surfaces of the martian meteorite ALH84001 contain abun dant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture sur faces also display carbonate globules. Contamination studies suggest t hat the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and in ternal structures of selected carbonate globules show that the globule s contain fine-grained, secondary phases of single-domain magnetite an d Fe-sulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Althou gh inorganic formation is possible, formation of the globules by bioge nic processes could explain many of the observed features, including t he PAHs. The PAHs, the carbonate globules, and their associated second ary mineral phases and textures could thus be fossil remains of a past martian biota.