NewsLife on Mars

Putative Martian Microbes Called Microscopy Artifacts

Science  05 Dec 1997:
Vol. 278, Issue 5344, pp. 1706-1707
DOI: 10.1126/science.278.5344.1706

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In the heated debate over the putative microfossils in martian meteorite ALH84001, most scientists have focused on arcane arguments about mineral isotopic compositions and formation temperatures, but for many, they simply look lifelike. Looks can be deceptive, however, and three meteoriticists now argue that there's nothing lifelike about the martian "bugs." Rather, they're simply a trick of the eye abetted by the peculiarities of the powerful microscopes used to image them. In a short paper in this week's Nature, this group presents its own nanometer-scale images of ALH84001. They argue that most of the "microfossils" are nothing more than narrow ledges of mineral protruding from the underlying rock that under certain viewing conditions can masquerade as fossil bacteria.