What was the original claim for life on Mars? August 15, 2010Posted by Simon in Uncategorized.
I thought it would be interesting to go back to the original 1996 paper that kicked off the whole controversy and see what it said. Here are some extracts:
“It is possible that all of the described features in ALH84001 can be explained by inorganic processes, but these explanations appear to require restricted conditions – for example, sulphate-reducing conditions in Antarctic ice sheets, which are not known to occur.”
“In examining the Martian meteorite ALH84001 we have found that the following evidence is compatible with the existence of past life on Mars:”
and the paper then proceeds to list 5 pieces of evidence that hint at possible life.
“None of these observations is in itself conclusive for the existence of past life. Although there are alternative explanations for each of these phenomena taken individually, when they are considered collectively, particularly in view of their spatial association, we conclude that they are evidence for primitive life on early Mars.”
All in all, it’s not what you would call a strong argument, and one that’s fairly easy to attack. Maybe this is the source of at least some of the controversy – people assume that the authors are saying “We found life on Mars” but what they really said was “We found some individual pieces of evidence that, when put together, are evidence for life on Mars”.
In my last post, I referred to David McKay speaking to a Stanford class in 2009 about ALH84001 – I’ve found it on YouTube here. At the 48:00 mark, he reiterates that any individual piece of evidence might be discredited, but the conclusion follows from the whole collection of evidence. You’ve got to give him credit for sticking to his story through 14 years of attacks on his argument!