Postprint version. Published in Current Opinion in Chemical Biology, Volume 4, Issue 2, April 1, 2000, pages 171-176. Copyright © 2000 Elsevier. The definitive version is available at http://dx.doi.org/10.1016/S1367-5931(99)00072-1.
Certain chemical and mineral features of the Martian meteorite ALH84001 were reported in 1996 to be probable evidence of ancient life on Mars. In spite of new observations and interpretations, the question of ancient life on Mars remains unresolved. Putative biogenic, nanometer magnetite has now become a leading focus in the debate.