A good summary of the ALH84001 controversy

Thanks to a tip from Erin, I’ve been reading this story from Astrobiology Magazine about ALH84001. It’s a good summary of the current state of things. The highlights for me were:

1. Kathie Thomas-Keprta, who has been involved in the research almost from the beginning, was originally invited into the team by David McKay to study the fossil-like objects with an electron microscope:

“I kind of thought he was crazy,” she says. “I thought I would join the group and straighten them out.”

She’s been with the group ever since, so clearly she’s changed her views on McKay and his research!

2. Allan Treiman of the Lunar and Planetary Institute, who had been critical of the research, said many other scientists have simply moved on to other things:

“I am one of the few holdovers still arguing about it,” he says. “I can’t move on.”

The debate may not be settled anytime soon. Treiman isn’t sure how one could ever entirely rule out that Martians might have had a hand in forming ALH84001. “Nature is infinitely complicated,” he says. “It is always surprising us.”

However, he believes the alternative explanations from geology and chemistry are simpler, since they don’t require inventing the whole new science of Martian biology. Scientists are trained to pick the simplest explanation.

A nice reference to using Occam’s Razor as the guiding principle when evaluating competing hypotheses.

3. Timothy Swindle from the University of Arizona used to run surveys of what other scientists thought about ALH84001:

An informal poll of more than 100 scientists by Swindle in 1997, right after the first announcement of possible biological relics in ALH84001, showed that most of the community was already hedging their bets. The typical response gave about even odds that Mars once had life but said that there was just a 1-in-5 chance that McKay’s group had found the smoking gun.

A few years later, Swindle tried to do the poll again but couldn’t get enough respondents to form a representative sample. He thinks most people had made up their mind that ALH84001 did not carry biosignatures from Mars. But that doesn’t mean that sifting through the meteorite hasn’t been worth it.

“It was good science,” he says. “It challenged people to really think about what would count as evidence of life on Mars.”

It’s worth noting that even though most scientists thought ALH84001 didn’t how signs of life, they were much more willing to believe that Mars did once have life. When you look at this controversy with Kuhn’s framework, it’s important to realise what the existing paradigm is – it’s *not* that Mars doesn’t (and can’t) have life; it’s that we don’t have any good evidence for Martian life.