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Accession Number N20120011767
Title Origin of Magnetite Crystals in ALH84001 Carbonate Disks.
Publication Date 2012
Media Count 2p
Personal Author D. S. McKay E. K. Gibson K. L. Thomas-Keprta S. J. Clemett S. J. Wentworth
Abstract Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks believed to have formed approx 3.9 Ga ago at beginning of the Noachian epoch. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe3O4) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. We have sought to resolve between these hypotheses through the detailed characterized of the compositional and structural relationships between the carbonate disks, their associated magnetites and the orthopyroxene matrix in which they are embedded. Comparison of these results with experimental thermal decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in the ALH84001 carbonate disks are not the products of thermal decomposition.
Keywords Carbonates
Chemical properties
Ion beams
Meteoritic composition
Meteoritic microstructures
Snc meteorites
Transmission electron microscopy
X ray spectroscopy

Source Agency National Aeronautics and Space Administration
NTIS Subject Category 54 - Astronomy & Astrophysics
84B - Extraterrestial Exploration
Corporate Author National Aeronautics and Space Administration, Houston, TX. Lyndon B. Johnson Space Center.
Document Type Conference proceedings
Title Note N/A
NTIS Issue Number 1226
Contract Number N/A

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