From: LARRY KLAES (ljk4@msn.com)
Date: Tue May 14 2002 - 07:30:35 PDT
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From: baalke@jpl.nasa.gov
Sent: Tuesday, May 14, 2002 2:21 AM
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Subject: Resolution of a Big Argument About Tiny Magnetic Minerals in Martian Meteorite
http://www.psrd.hawaii.edu/May02/ALH84001magnetite.html
Resolution of a Big Argument About Tiny Magnetic Minerals in Martian Meteorite
--- Magnetic minerals in Martian meteorite
ALH 84001 formed as a result of impact
heating and decomposition of carbonate; they
were never used as compasses by Martian
microorganisms.
Written by Edward R. D. Scott (Hawai'i Institute of Geophysics and Planetology)
and David J. Barber (Cranfield University and University of Greenwich)
Planetary Science Research Discoveries
May 13, 2002
Tiny grains of magnetite, an iron oxide mineral, from a Martian meteorite
are markedly similar in size, shape, and composition to the little oxide
magnets used by bacteria on Earth and different from other naturally formed
magnetites. Is this good evidence for life on Mars? Or did the Martian
magnetite grains form by another process? Our studies reveal that the planes
of atoms in the Martian magnetites are aligned with atomic planes in the
carbonate in which the magnetites are embedded. This shows that the
magnetites formed in the rock and not inside microorganisms.
References:
Barber, D. J. and Scott, E. R. D. (2002) Origin of supposedly biogenic
magnetite in the Martian meteorite Allan Hills 84001. Proceedings of
the National Academy of Sciences 99, 6556-6561.
Thomas-Keprta, K. L., Clement, S. J., Bazylinski, D. A., Kirschvink, J.
L., McKay, D. S., Wentworth, S. J., Vali, H., Gibson, E. K., Jr.,
McKay, M. F., and Romanek, C. S. (2001). Truncated hexa-octahedral
magnetite crystals in ALH 84001: presumptive biosignatures. Proceedings
of the National Academy of Sciences 98, 2164-2169.
Full story here:
http://www.psrd.hawaii.edu/May02/ALH84001magnetite.html
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