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Search for Past Life on Mars: Possible Relict Biogenic Activity in Martian Meteorite ALH84001Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest the PAHs are indigenous to the meteorite. 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 Fe-monosulfides. The carbonate globules are similar in texture and size to some terrestrial bacterially induced carbonate precipitates. Although inorganic formation is possible, formation of the globules by biogenic processes could explain many of the observed features including the PAHs. The PAHs, the carbonate globules, and their associated secondary mineral phases and textures could thus be fossil remains of a past martian biota.
Document ID
Document Type
Preprint (Draft being sent to journal)
McKay, David S. (NASA Johnson Space Center Houston, TX United States)
Gibson, Everett K., Jr. (NASA Johnson Space Center Houston, TX United States)
Thomas-Keprta, Kathie L. (Lockheed Martin Corp. Houston, TX United States)
Vali, Hojatollah (McGill Univ. Montreal, Quebec Canada)
Romanek, Christopher S. (Georgia Univ. Aiken, SC United States)
Clemett, Simon J. (Stanford Univ. CA United States)
Chillier, Xavier D. F. (Stanford Univ. CA United States)
Maechling, Claude R. (Stanford Univ. CA United States)
Zare, Richard N. (Stanford Univ. CA United States)
Date Acquired
September 6, 2013
Publication Date
August 1, 1996
Publication Information
Publication: Science
Subject Category
Space Biology
Report/Patent Number
NAS 1.15:111753
Funding Number(s)
PROJECT: RTOP 185-52-11-01
Distribution Limits
Work of the US Gov. Public Use Permitted.

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