Morphological Evidence for an Exclusively Inorganic Origin for Magnetite in Martian Meteorite Alh84001

Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures.

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 (Fe(3)O(4)) 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, bi...

Thermal Decomposition of an Impure (roxbury) Siderite: Relevance to the Presence of Chemically Pure Magnetite Crystals in Alh84001 Carbonate Disks

Background and Introduction: The question of the origin of nanophase magnetite in Martian meteorite ALH84001 has been widely debated for nearly a decade. Golden et al. [1] have reported producing nearly chemically pure magnetite from thermal decomposition of chemically impure siderite [(Fe, Mg, Mn)CO3]. This claim is significant for three reasons: first, it has been argued that chemically pure ...

Elongated prismatic magnetite crystals in ALH84001 carbonate globules: potential Martian magnetofossils.

Using transmission electron microscopy (TEM), we have analyzed magnetite (Fe3O4) crystals acid-extracted from carbonate globules in Martian meteorite ALH84001. We studied 594 magnetites from ALH84001 and grouped them into three populations on the basis of morphology: 389 were irregularly shaped, 164 were elongated prisms, and 41 were whisker-like. As a possible terrestrial analog for the ALH840...

Mechanisms of Formation of Magnetite in Martian Meteorite Alh84001

Origins of magnetite nanocrystals in Martian meteorite ALH84001

The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throu...