But most specialists in the analysis of the tiny minerals being offered in evidence remain skeptical. Now, the attention has shifted to minuscule grains of the iron mineral magnetite, the same sorts of particles that some earthly bacteria form in long chains to act as a magnetic compass. Other researchers agreed about the resemblance but concluded the evidence was not extraordinary enough to prove such an extraordinary claim. In the second PNAS paper, Imre Friedmann of NASA's Ames Research Center at Moffett Field, California, and colleagues contend that the arrangement of magnetite in ALH84001 argues for ancient life as well. Microscopists who have seen the published images are not so sure.
Iron oxides are all over the place.
It's the interpretation as bacterial chains that scares me. Something besides bacteria, something nonliving, might well have made the apparent chains, he says. Microscopist John Bradley of the private research firm MVA Inc. in Norcross, Georgia, agrees.