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Skeptics prepare to challenge Mars revelation

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August 7, 1996
Web posted at: 10:50 p.m. EDT

From Correspondent Ann Kellan

ATLANTA (CNN) -- When NASA said it had found evidence of life on Mars in a 4 1/2 billion-year-old rock, the world sat up and took notice.

Now, the scientific process is kicking in, as the rest of the scientific community begins its own analysis. NASA's findings may be validated -- or they may be ripped to shreds.

While most scientists agree on the meteorite's origin and age, skeptics raise an eyebrow when it comes to saying the rock proves that life once existed on Mars. Even the study's authors back away from claiming life was definitely present.

"We have a number of forms which it is very tempting for us to interpret as Martian microfossils, but we have no confirming evidence," said David McKay of the Johnson Space Center.

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Laser analyzers helped scientists detect organic chemicals called PAHs -- polycyclic aromatic hydrocarbons -- in the meteorite. When living material degrades, it leaves behind PAHs. And here's where skeptics have a problem: PAHs are common in the universe and not always linked to living material.

"They are found all over the place on the earth," said Robert Clayton, a professor of chemistry at the University of Chicago.

"These same authors who have been working with these meteorites have found them on other kinds of meteorites, found them in interstellar dust particles, and it's not clear how they get formed, but they are everywhere. So, I think finding these in Mars by itself is not in any sense evidence of life."

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The study's authors say there's a checklist of conditions that led to their findings. The meteorite was accurately dated, microscopic fossils of bacteria were present, biominerals were present in the organisms, and the PAHs provide proof of complex chemicals.

"So, from the criteria we have, we come to the conclusion that we meet a large number, if not all, of the criteria which we use to establish evidence of past life," said Everett Gibson of the Johnson Space Center.

Skeptics say what they've seen is not enough. They say it would be difficult for scientists to know what a living organism on Mars would look like.

"There is no evidence there is a cavity within them, a compartment, a cell," said Professor William Schopf, an expert on ancient bacteria at UCLA. "Why do you need that? Well, that is where the juices of a living organism reside, that's where the chemistry that makes things live works."

Scientists are currently working with a slice of the meteorite that is 1/500th of a hair in diameter, but they want to make it even smaller.

They say more sophisticated laser equipment will let them cut the meteorite down even more -- and lead to new research that will eventually help verify whether life ever existed on Mars.

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