Truncated hexa-octahedral magnetite crystals in ALH84001: Presumptive biosignatures

AUTOR(ES)

Thomas-Keprta, Kathie L.

FONTE

The National Academy of Sciences

RESUMO

McKay et al. [(1996) Science 273, 924–930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe3O4) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.

Documentos Relacionados

• Chains of magnetite crystals in the meteorite ALH84001: Evidence of biological origin
• Magnetic tests for magnetosome chains in Martian meteorite ALH84001
• Magnetofossils from Ancient Mars: a Robust Biosignature in the Martian Meteorite ALH84001
• Origin of supposedly biogenic magnetite in the Martian meteorite Allan Hills 84001
• Nucleotide sequence of the hexA gene for DNA mismatch repair in Streptococcus pneumoniae and homology of hexA to mutS of Escherichia coli and Salmonella typhimurium.