AS 1996 draws to a close, those heady days of summer seem like a dream. In August, scientists led by NASA's David McKay stunned the world by producing evidence of past life on Mars. But now two new analyses could put the final nail in the coffin of that claim.
The evidence for Martian life centres on the meteorite ALH84001, which chipped off the surface of Mars some 15 million years ago and landed in the Allan Hills region of Antarctica about 13 000 years ago (This Week, 17 August, p 4).
Fissures in the meteorite contain carbonate globules. Inside these are tiny tubular structures that look like fossilised bacteria. The globules also contain crystals of the minerals magnetite and iron sulphide that are similar to those produced by some terrestrial bacteria, and polycyclic aromatic hydrocarbons (PAHs), oily organic molecules often formed during the decomposition of living ...
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