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The initial response to the ALH84001 claim September 16, 2010

Posted by Simon in Uncategorized.

The response to the original ALH84001 paper was swift and cautious, at best.

In the same issue of Science as the original paper, there was a news article describing the initial reaction. Clearly the editors of the journal were already aware at this point of how controversial the issue would become. The headline was “Ancient Life on Mars? A meteorite has yielded evidence – but not proof – of ancient life on Mars. The claim has excited skeptical fascination among scientists but has made no converts so far”

In addition to quoting people on both sides of the debate:

“I think it’s very unlikely they have remnants of biological activity,” says William Schopf of the University of California, Los Angeles, who has spent his career separating microfossils of early life on Earth from imposters.

“I’m not convinced,” says interplanetary dust particle specialist Donald Brownlee of the University of Washington, “but I think they have made a credible case that these things could be microfossils. It’s unprecedented. It’s one of the most important things in science, it it’s true. [Exobiology] is intellectually interesting, but without any data, it’s just speculation; I think there’s some data now.”

The article concluded by warning that the issue would not be resolved for some time:

Don’t expect this drama to be wrapped up in the next TV season. The sort of supporting evidence that would convince Schopf and other critics could be slow in coming. As Schopf quoted Cornell exobiologist Carl Sagan: “Extraordinary claims require extraordinary evidence.”

Within a couple of months, the attacks were ramping up.  Edward Anders from the University of Chicago wrote this:

David S McKay et al. deserve praise for discovering possible evidence of past Martian life. The identification of indigenous organic compounds in a Martian meteorite alone is a breakthrough, reopening the possibility of life after the chill cast by Viking. The characterization of the carbonate globules sets a new standard for study of extraterrestrial materials.

After this polite opening, he gets down to the business of attacking the original paper. He concludes with this:

McKay et al. conclude their paper by listing five lines of evidence and then stating:

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, particularly in view of their spatial association, we conclude that they are evidence for primitive life on early Mars.

For all these observation, an inorganic explanation is at least equally plausible, and, by Occam’s Razor, preferable. Consistency arguments alone – weak consistency arguments especially – cannot strengthen, let alone prove, an extraordinary conclusion.

This wasn’t a case where a few strange results appear and are ignored until there’s enough of them that a crisis happens; the controversy existed in its full form right from day 1.



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