It has been the longest break in the short life of this blog. After a great Thanksgiving I cleaned out my grad student office and drove the load back to my new home. I've been organizing papers for a few days now.
One of the famous ALH 84001 SEM images, showing the chain-like series of crystals which McKay et al. (1996) suggested were biogenic.
In the world of planetary science, there are two new publications on the possibility of Martian fossils in meteorite ALH 84001. You may recall that in 1996 Dave McKay and his coauthors
revealed possible evidence for past life in the sample. They found carbonate and nanophase magnetite
(Fe3O4) mineral grains which, based on the minerals' occurrence, texture, and association with organic molecules, they suggested may have been deposited by bacteria. This was contentious, and still is -- many argued that the minerals had an inorganic origin -- but the hypothesis was never disproved. The new papers, found here and here, argue that the primary alternative hypothesis -- that the unusual magnetite textures formed during the impact shock that sent the rock Earthwards -- is not viable.
I read about the new work at New Scientist and The Martian Chronicles but I'm still working through the journal articles. It all came as quite a coincidence, because I just started reading Kathy Sawyer's book The Rock From Mars which details the escalation of the scientific debate that began in 1996, and it's enough for now to say that it quickly got bitter and personal. I was going to post about the sometimes all-too-human workings of the science world when I finished reading it, but now I feel I should hurry up and put it all in context with the new papers. I'll get on it -- in the meantime, there's a huge amount of information on the topic online beyond what I've linked to above, if you're interested.
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