Scientists doubt meteorite carried life to Earth

March 7, 2011

Joe Palca

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Could life have rained down on Earth from outer space? That tantalizing prospect has been raised in a new scientific paper by NASA scientist Richard B. Hoover of the Marshall Space Flight Center in Huntsville, Ala. The only problem with the research seems to be that most scientists who have seen the work think it's probably wrong.

The paper argues that microscopic filaments Hoover sees in carbonaceous meteorites were made by bacteria in the meteorite before it fell to Earth.

But there are other explanations, too.

"There are all sorts of chemical processes that lead to spheres and hollow balls and filaments," says George Cody, a geochemist at the Carnegie Institution for Science. And even if the shapes are signs of long-dead microorganisms, Cody says, it's hard to be certain any signs of life in a meteorite found on Earth came from outer space.

"More likely than not, if you didn't take extraordinary precaution ... they'd be quickly infected by both [terrestrial] fungal microorganisms and bacteria," he says.

Hoover wasn't available to comment, so it's hard to know his motivations. But it's not hard to understand why a scientist would want to share what he thinks is a dramatic discovery with the world.

"Scientists are discovery junkies," says Robert Hazen, a colleague of Cody's at the Carnegie Institution.

"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.' "

Skepticism Is Key

But skepticism is crucial. Fifteen years ago, another group of scientists claimed they saw signs of life in a meteorite from Mars recovered in Antarctica. The media hoopla accompanying that paper was, perhaps, more justified, since the claim had been more thoroughly vetted by other scientists, and NASA held a press conference trumpeting the results.

A few years later, most scientists were convinced the finding was wrong. And this time, NASA wants nothing to do with the new claims of life.

Hazen says a finding that proves to be wrong isn't necessarily a bad thing.

"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," he says.

And Hazen admits there's a small chance this new report is correct.

"There have been some extraordinary claims in the past that have been right," he says. "It takes years to confirm they are right, but once in a while, they are."

Hazen is sure of one thing: If the new claim is wrong "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," he says, and eventually close in on the truth. Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.