Scientists dispute NASA's claims about Mars meteorite
January 15, 1998
Web posted at: 9:25 p.m. EST (0225 GMT)
From Reporter Rick Lockridge
SAN DIEGO (CNN) -- Last year, NASA scientists trumpeted the news that a potato-sized meteorite found in Antarctica contained evidence that there may have once been life on Mars.
And while those scientists continue to stand behind that theory, others who have examined the rock say organic matter found on the meteorite more likely came from earthly contamination, rather than ancient Martian life.
"This problem of contamination is a real issue and, I think, is a serious challenge to any claims that there's organic compounds in this meteorite that came from Mars," says biochemist Jeffrey Bada of the Scripps Institution of Oceanography.
The rock in question is a chunk of Mars that was blasted away from the red planet by a comet or asteroid. It sailed through the solar system for perhaps millions of years before falling to Earth in Antarctica 13,000 years ago.
NASA scientists say the rock contains several tantalizing clues that primitive life once existed on Mars, including greasy compounds called polycyclic aromatic hydrocarbons, or PAHs, which they describe as the residue of life.
"We have studied these in great detail, and we still believe (the PAHs) come from Mars, not from Antarctica," says David McKay of NASA, who did the initial study of the Mars rock.
NASA scientists say the meteorite contains evidence of ancient life on Mars
But Bada says PAHs are "rock chemicals," not chemicals that would indicate the presence of life.
"If you're going to look at potential clues for life on Mars, you should go right to the compounds that play an essential role in biochemistry as we know it," Bada said.
And Bada says he and his colleagues have run through test after test, looking for amino acids, which are building blocks for life. While they found amino acids on the rock, those chemicals closely resembled amino structures already found on Earth.
The explanation that Bada's team has developed is that the meteorite was contaminated with those amino acids while in Antarctica. NASA scientists concede that the rock was contaminated. But they say that doesn't change their conclusions about the meteorite.
Scientists have run tests looking for amino acids, the building blocks of life
For one thing, while the rock was contaminated with forms of carbon that are clearly from Earth, an analysis also turned up a mystery form of carbon that could be extraterrestrial in origin. And carbon is one of the basic chemical building blocks of life.
More analysis of that carbon is under way. In the meantime, no one involved in this debate is wavering an inch.
"People have become entrenched in their views on this, especially the original researchers," said Bada. "And I think in their minds they have definite proof. I don't agree with that."
"We're absolutely standing behind our position at this point," McKay said.
NASA plans to send an unmanned probe to Mars by the year 2008 to bring back fresh rocks from the red planet. Only then might this debate be settled.