BACTERIAL MINERALIZATION PATTERNS IN BASALTIC AQUIFERS - IMPLICATIONSFOR POSSIBLE LIFE IN MARTIAN METEORITE ALH84001

To explore the formation and preservation of biogenic features in igne ous rocks, we have examined the organisms in experimental basaltic mic rocosms using scanning and transmission electron microscopy, Four type s of microorganisms were recognized on the basis of size, morphology, and chemical composition, Some of the organisms mineralized rapidly, w hereas others show no evidence of mineralization. Many mineralized cel ls are hollow and do not contain evidence of microstructure. Filaments , either attached or no longer attached to organisms, are common. Unat tached filaments are mineralized and are most likely bacterial appenda ges (e,g., prosthecae). Features similar in size and morphology to una ttached, mineralized filaments are recognized in martian meteorite ALH 84001.