Evidence for exclusively inorganic formation of magnetite in Martian meteorite ALH84001

@article{Golden2004EvidenceFE,
  title={Evidence for exclusively inorganic formation of magnetite in Martian meteorite ALH84001},
  author={D. C. Golden and Doug W. Ming and Richard V. Morris and Adrian J. Brearley and Howard V. Lauer and Allan H. Treiman and Michael. E. Zolensky and Craig S. Schwandt and Gary E. Lofgren and Gordon Mckay},
  journal={American Mineralogist},
  year={2004},
  volume={89},
  pages={681 - 695}
}
Abstract Magnetite crystals produced by terrestrial magnetotactic bacterium MV-1 are elongated on a [111] crystallographic axis, in a so-called “truncated hexa-octahedral” shape. This morphology has been proposed to constitute a biomarker (i.e., formed only in biogenic processes). A subpopulation of magnetite crystals associated with carbonate globules in Martian meteorite ALH84001 is reported to have this morphology, and the observation has been taken as evidence for biological activity on… 
Magnetite as a prokaryotic biomarker: A review
[1] Over the years, nanometer-sized magnetite (Fe3O4) crystals have been recovered from many modern and ancient environments including sediments and soils and even meteorites. In some cases these
Experimental shock decomposition of siderite and the origin of magnetite in Martian meteorite ALH 84001
Abstract Shock recovery experiments to determine whether magnetite could be produced by the decomposition of iron‐carbonate were initiated. Naturally occurring siderite was first characterized by a
Biomimetic Properties of Minerals and the Search for Life in the Martian Meteorite ALH84001
The existence of extraterrestrial life was heralded by controversial claims made in 1996 that the Martian meteorite ALH84001 harbored relics of ancient microorganisms. We review here the accumulated
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References

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TLDR
It is suggested that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process and are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.
Magnetofossils from Ancient Mars: a Robust Biosignature in the Martian Meteorite ALH84001
TLDR
It is argued that these Martian magnetite crystals found within carbonate globules and their associated rims in the meteorite are in fact magnetofossils, which would constitute evidence of the oldest life forms known.
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    Proceedings of the National Academy of Sciences of the United States of America
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TLDR
All occurrences of magnetite and periclase are entirely consistent with in situ growth by solid-state diffusion as a result of carbonate decomposition during impact heating.
Elongated prismatic magnetite crystals in ALH84001 carbonate globules: potential Martian magnetofossils.
Epitaxial growth of nanophase magnetite in Martian meteorite Allan Hills 84001: Implications for biogenic mineralization
TLDR
Epitaxy rules out intracellular precipitation of these magnetites by (Martian) organisms, provides further evidence of the high-temperature (> 120 degrees C) inorganic origins of magnetite in ALH 84001, and indicates that the carbonates also have been exposed to elevated temperatures.
Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.
Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive
Structural and morphological anomalies in magnetosomes: possible biogenic origin for magnetite in ALH84001
TLDR
Observations demonstrate that the structures of the magnetite particles in ALH84001, their spatial arrangement and coprecipitation with carbonates and proximity to silicates are consistent with being biogenic.
Letter. A simple inorganic process for formation of carbonates, magnetite, and sulfides in martian meteorite ALH84001
Abstract We show experimental evidence that the zoned Mg-Fe-Ca carbonates, magnetite, and Fe sulfides in Martian meteorite ALH84001 may have formed by simple, inorganic processes. Chemically zoned
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TLDR
It is argued that the existing crystallographic and morphological evidence is inadequate to support the inference of former life on Mars, and three-dimensional shapes of nanocrystals can be defined.
Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001
TLDR
High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and iron sulfides.
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