Main Question or Discussion Point
Are micro-organisms fossils on so-called Martian meteorite true? I think it is more likely contaminated by life on Earth...
Interest in SNC meteorites was recently rekindled by the announcement from researchers at Stanford University and NASA's Johnson Space Flight Center that careful analysis of the ALH84001 meteorite had yielded evidence of ancient bacteria-like life forms on Mars. This work was set to appear in an issue of the journal Science but was leaked to the press on August 6, 1996. The resulting surge of interest led to a NASA press release on Aug. 7, 1996 followed by a press conference. The resulting tumult precipitated a flurry of media and NASA public relations activity which included a front-page story in The New York Times (Wilford 1996).
Using scanning electron microscopy and laser mass spectroscopy, a team led by David S. McKay identified polycyclic aromatic hydrocarbons (PAHs) in the meteorite, as well as globules of carbonate and the minerals magnetite and iron sulfide. The carbonate globules are small elongated features resembling similar ones found on Earth which are believed to have formed in association with bacteria. McKay et al. (1996) determined their age to be approximately 3.6 billion years. All the unusual compounds found in the meteorite are associated with bacterial activity on Earth, PAHs with decay products of microorganisms and magnetite and iron sulfide with anaerobic bacteria. However, the presence of these compounds is not necessarily diagnostic for the presence of bacteria. McKay and his coworkers appear to have excluded the possibility that any of their discoveries represent terrestrial contamination, so the constituents they describe presumably must have formed while the meteorite was still on the surface (or shallow subsurface) of Mars.
While the reported discoveries are intriguing and consistent with formation through biological activity (especially when taken together), this conclusion requires additional confirmation. It should be recalled that initial experiments on soil samples from one of the Viking landers were heralded as clear evidence of organic material, whereas subsequent laboratory work showed that the observed results could be reproduced with entirely inorganic soil constituents. While the presence of past life on Mars would be a scientific discovery of epic proportions and warrants the closest possible scrutiny, it is premature at this juncture to state that the existence of life on Mars, past or present, has been conclusively demonstrated.