HR: 13:55h
AN: GP22A-02 INVITED     [PDF]
TI: Magnetic Tests For Magnetosome Chains In Martian Meteorite ALH84001
AU: * Weiss, B P
EM: bweiss@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, M.S. 170-25, 1200 East California Blvd., Pasadena, CA 91125 United States
AU: * Weiss, B P
EM: bweiss@gps.caltech.edu
AF: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Bldg. 54, Cambridge, MA 02139 United States
AU: Kim, S
EM: soonsam.kim@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, M.S. 183-401, Pasadena, CA 91109 United States
AU: Kirschvink, J L
EM: kirschvink@caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, M.S. 170-25, 1200 East California Blvd., Pasadena, CA 91125 United States
AU: Sankaran, M
EM: mohan@its.caltech.edu
AF: Division of Chemistry and Chemical Engineering, California Institute of Technology, M.S. 210-41, 1200 East California Blvd., Pasadena, CA 91125 United States
AU: Kobayashi, A
EM: kobayashi-a@aist.go.jp
AF: Division for Human Life Technology, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka, 563-8577 Japan
AU: Komeili, A
EM: komeili@gps.caltech.edu
AF: Division of Geological and Planetary Sciences, California Institute of Technology, M.S. 170-25, 1200 East California Blvd., Pasadena, CA 91125 United States
AB: Transmission electron microscopy studies have been used to argue that magnetites in carbonates from Martian meteorite ALH84001 have a composition and morphology indistinguishable from that of magnetotactic bacteria and their magnetofossils (1). It has even been claimed from scanning electron microscopy imaging that some ALH84001 magnetites are aligned in chains (2). If true, this would provide dramatic support for the magnetofossil hypothesis because alignment in chains is perhaps the most distinctive of the six crystallographic properties thought to be collectively unique to magnetosomes. The leading alternative hypothesis is that the ALH84001 magnetites are the inorganic products of shock-heating of the carbonates (3, 4). Here we use three rock magnetic techniques-low-temperature cycling, the Moskowitz test (5), and ferromagnetic resonance (FMR)-to demonstrate that most or all of the magnetites in ALH84001 are unusually pure and fine-grained but are not arranged in magnetosome chains. 1. K. L. Thomas-Keprta et al., Geochim. Cosmochim. Acta 64, 4049-4081 (2000). 2. I. E. Friedmann, J. Wierzchos, C. Ascaso, M. Winklhofer, Proc. Natl. Acad. Sci. USA 98, 2176-2181 (2001). 3. D. C. Golden et al., Am. Mineral. 83, 370-375 (2001). 4. D. J. Barber, E. R. D. Scott, Proc. Natl. Acad. Sci. USA 99, 6556-6561 (2002). 5. B. M. Moskowitz, R. B. Frankel, D. A. Bazylinski, Earth Planet. Sci. Lett. 120, 283-300 (1993).
DE: 1505 Biomagnetism
DE: 1519 Magnetic mineralogy and petrology
DE: 5440 Magnetic fields and magnetism
DE: 6225 Mars
DE: 6240 Meteorites and tektites
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting