MELISSA BLOCK, Host:
But as NPR science correspondent Joe Palca reports, extraordinary claims require extraordinary proof. And in this case, the proof is lacking.
JOE PALCA: This isn't the first time NASA scientist Richard Hoover has claimed to see signs of life in so-called carbonaceous meteorites, a kind of meteorite rich in the chemical building blocks of life. Why this particular paper and not others gained attention is one of those media mysteries. The main thrust of the paper is that a microscopic evaluation of these carbonaceous meteorites shows that they contain filaments that might have been made by a living organism, such as bacteria. But there are other explanations too.
GEORGE CODY: There are all sorts of chemical processes that lead to spheres and hollow balls and filaments.
PALCA: George Cody is a geochemist at the Carnegie Institution for Science. In addition to chemical processes, Cody says it's hard to be certain that any signs of life you do see in meteorites found on Earth came from outer space.
CODY: So it's more likely than not that if you didn't take, you know, extraordinary precaution that, in fact, they'd be quickly infected by both fungal microorganisms and bacteria as well.
PALCA: So, in other words, you pick this thing up off the ground and, almost immediately, even from the bacteria and fungus on your hands, if you're not careful, you've contaminated the sample.
CODY: Absolutely. It would be probably completely unavoidable.
PALCA: Robert Hazen is a colleague of Cody's at the Carnegie Institution.
ROBERT HAZEN: What you got to remember is scientists are discovery junkies. They always want to discover something new, that's why we're in the game. And if you discover something that seems like it might be extraordinary, there's this human nature - you tend to think, wow, I made this great discovery, as opposed to this can't be right.
PALCA: Hazen says a finding that proves to be wrong isn't necessarily a bad thing.
HAZEN: We've learned so much from what was basically a bunch of Mars meteorites that don't have any compelling evidence for life, but they sure have some fascinating chemistry.
PALCA: Hazen admits there's a small chance this new report is correct.
HAZEN: There have been some extraordinary claims in the past that turned out to be right. It takes years to confirm that they're right, but once in a while, they are.
PALCA: Hazen is sure of one thing: If the new claim is wrong...
HAZEN: It will be corrected. There's no question about it. Science will come up with the correct explanation for these filament-like structures, and we'll move on.
PALCA: Joe Palca, NPR News, Washington.
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