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Published June 1, 2004 | Published
Journal Article Open

Magnetic tests for magnetosome chains in Martian meteorite ALH84001


Transmission electron microscopy studies have been used to argue that magnetite crystals in carbonate from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria. It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetite crystals are aligned in chains. Alignment of magnetosomes in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetofossils. Here we use three rock magnetic techniques, low-temperature cycling, the Moskowitz test, and ferromagnetic resonance, to sense the bulk composition and crystallography of millions of ALH84001 magnetite crystals. The magnetic data demonstrate that although the magnetite is unusually pure and fine-grained in a manner similar to terrestrial magnetofossils, most or all of the crystals are not arranged in chains.

Additional Information

© 2004 by the National Academy of Sciences. Communicated by Norman H. Sleep, Stanford University, Stanford, CA, March 31, 2004 (received for review August 7, 2003). Published online before print May 20, 2004, 10.1073/pnas.0402292101 We thank T. Bosak for helpful advice and N. H. Sleep for communicating this manuscript. S.S.K. and the ferromagnetic resonance measurements were supported by the Mars Instrument Development Project Program; R.E.K. was supported by a National Science Foundation Graduate Research Fellowship; A. Komeili was supported by a Beckman Senior Research Fellowship; and B.P.W. and J.L.K. were supported by the National Aeronautics and Space Administration Exobiology Program and the National Aeronautics and Space Administration Astrobiology Institute.

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