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Rock may not indicate life on Mars, team says

SHARE Rock may not indicate life on Mars, team says

A California research team says that a telltale chemical signature suggests strongly that minerals inside a rock from Mars are not evidence of life on the Red Planet.

In a study published this week in the journal Science, University of California, San Diego, scientists said that mineral structures inside the rock bear chemical traces left by nonbiologic processes, and not by ancient bacteria as proposed by some researchers at the National Aeronautics and Space Administration.A space agency scientist says the research is flawed and does not prove that microbes never lived inside the rock known as Allen Hills 84001.

Mark Thiemens, a professor of chemistry at the University of California, said his team analyzed the isotopic characteristics of oxygen found inside the rock and concluded that it was deposited there from the carbon dioxide and ozone of the Martian atmosphere.

Thiemens said that if the oxygen in the mineral structure had been deposited by a microbe or other life form, the chemical signature would have matched that of oxygen in water, not oxygen in the atmosphere. Life, as it is now understood, depends on water and would leave behind a chemical residue of oxygen that was once in water.

"If these things were biogenic, they should have equilibrated (chemically matched) with water," said Thiemens. "They didn't. They equilibrated with the atmosphere."

He said the finding does not give final proof that the rock never contained life, but "it is a significant" argument against the NASA theory.

Everett Gibson, a NASA researcher at the Johnson Space Center in Houston and co-author of the theory that Mars once held life, said that Thiemens and his team may not have tested the precise structures in the rock that the NASA scientists believe were formed by life.

Traces of life found in the rock are visible only with powerful microscopes and not easily measured, said Gibson.

He said the Thiemens group used a crushed sample from the Mars rock that may have included other minute bits of minerals that distorted the chemical findings.

Thiemens said that a new study is under way in which an even smaller specimen will be analyzed and the results of that, he said, "will give definitive evidence that is pretty close" to a final answer.

The rock has been identified as originating on Mars. It is believed that the rock was smashed into space when the Red Planet collided with an asteroid. The Mars rock is thought to have spent millions of years in orbit before falling to Earth several thousand years ago. It was found in an ice field, called Allen Hills, in Antarctica.

Gibson and his colleagues analyzed the rock at the moon rock laboratory in Houston and concluded that some mineral structures, called carbonates, were evidence that the microbes lived in the rock before it was blasted away from Mars.