Many scientists were justifiably skeptical about those tiny, worm-like shapes seen in Martian meteorite ALH84001. Said to be fossilized bacteria, the objects seemed much too small to be viable. Some experts suggested they were just abiotic crystal-line growths. K.L. Thomas-Keprta, who led the NASA team studying ALH84001, snorted that her group was not so stupid that it would mistake crystals for fossils. (SF#116)
Thomas-Keprta et al have now come forward with more evidence that ALH-84001 does indeed contain biogenic material. Those worm-like forms have iron-rich rims containing fine-grained crystals of magnetite, some of which possess a unique morphology and which are essentially identical to the magnetite crystals secreted by magnetotactic bacteria on earth. Their conclusion:
In ALH84001, the presence of these elongated prismatic magnetite crystals embedded within the carbonate glo-
bules, which clearly formed on Mars, represents strong evidence for life on early Mars.
(Thomas-Keprta, Kathie L., et al; "Biogenic Magnetite within Martian Meteorite ALH84001," Eos, 80:F69, 1999.)