title: Magnetite morphology and life on Mars.
abstract: Nanocrystals of magnetite (Fe(3)O(4)) in a meteorite from Mars provide the strongest, albeit controversial, evidence for the former presence of extraterrestrial life. The morphological and size resemblance of the crystals from meteorite ALH84001 to crystals formed by certain terrestrial bacteria has been used in support of the biological origin of the extraterrestrial minerals. By using tomographic and holographic methods in a transmission electron microscope, we show that the three-dimensional shapes of such nanocrystals can be defined, that the detailed morphologies of individual crystals from three bacterial strains differ, and that none uniquely match those reported from the Martian meteorite. In contrast to previous accounts, we argue that the existing crystallographic and morphological evidence is inadequate to support the inference of former life on Mars.
authors.affiliation: Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-1404, USA. pbuseck@asu.edu
authors.forename: P R
authors.initials: PR
authors.lastname: Buseck
authors.forename: R E
authors.initials: RE
authors.lastname: Dunin-Borkowski
authors.forename: B
authors.initials: B
authors.lastname: Devouard
authors.forename: R B
authors.initials: RB
authors.lastname: Frankel
authors.forename: M R
authors.initials: MR
authors.lastname: McCartney
authors.forename: P A
authors.initials: PA
authors.lastname: Midgley
authors.forename: M
authors.initials: M
authors.lastname: Pósfai
authors.forename: M
authors.initials: M
authors.lastname: Weyland
mesh_terms: D005118:Extraterrestrial Environment; D052203:Ferrosoferric Oxide; D007501:Iron; D010087:Oxides
chemical_list: D010087:Oxides; D007501:Iron; D052203:Ferrosoferric Oxide