HOUSTON, Aug 6, 1996 (Reuter) - A team of U.S. scientists have discovered evidence of ancient, single-cell life on Mars in remains from a meteorite that plunged to Earth 13,000 years ago, NASA officials said on Tuesday.
A consortium of space agency and university scientists said microfossil remains in the meteorite indicated a primitive form of life may have existed on Mars billions of years ago, NASA administrator Daniel Goldin said.
"NASA has made a startling discovery that points to the possibility that a primitive form of microscopic life may have existed on Mars more than three billion years ago," Goldin said.
The meteorite, found in the frozen fields of Antarctica in 1984, was blasted away from Mars by the impact of an asteroid about 16 million years ago, the scientists said in a draft of an article prepared for Science magazine obtained by Reuters.
The researchers discovered preliminary evidence of organic, carbon-based molecules on the meteorite, which crystallised from the molten rock of a volcano about 4.5 billion years ago on the surface of Mars, the article said.
Looking for signs of organic, carbon-based molecules -- the building blocks of life on Earth -- the scientists found polycyclic aromatic hydrocarbons inside tiny fractures in the meteorite that formed nearly a billion years after the rock cooled.
"What they've got is a meteorite which has been altered at fairly low temperatures, and what they are saying is that the alteration may be due to organic activity," said Arch Reid, a geosciences professor at the University of Houston.
When the meteorite was blasted off the surface of Mars and into space, it may have carried with it to Earth the first evidence of life on that planet, he said.
"The significance is that we have no direct evidence right now other than this possibility that there ever was life on Mars," Reid said.
Scientists cautioned against people envisioning Hollywood-inspired creatures from outer space, saying the organisms appear to be more like simple bacteria found here on Earth.
"I want everybody to know that we are not talking about 'little green men,'" NASA's Goldin said. "These are extremely small, single-cell structures that somewhat resemble bacteria on Earth. There is no evidence or suggestion that any higher life form ever existed on Mars."
Although the Viking lander experiments in 1976 found no signs of life, the discovery that water once flowed on the now-dead planet has supported theories that life would eventually be found on Mars and elsewhere.
"It makes it very promising there may be life in other solar systems," biochemist Stanley Miller at the University of California at San Diego said of the NASA findings. "What it really does show is the formation of life on a planet can take place rather easily."
Researchers at the Johnson Space Centre in Houston were the first to theorise that a collection of a dozen meteorites found in Antarctica contained chemical composition and gases consistent with the environment on Mars.
The researchers about two years ago discovered that another meteorite in the collection, catalogued as Allan Hills 84001 or ALH84001, also was from Mars. It was that specimen that yielded the preliminary evidence of primitive life on Mars, the scientists said.
"Our objective was to look for signs of past fossil life within the pore space or secondary minerals of the Martian meteorites," NASA scientist David McKay said in the Science article. "Our task is difficult because we have only a small piece of rock from Mars and we are searching for Martian biomarkers on the basis of what we know about life on Earth."
McKay authored the Science article along with researchers from Stanford University, the University of California-Los Angeles and Lockheed-Martin Corp.
The scientists plan to publish their findings in the August 16 issue of Science magazine and will discuss their findings publicly for the first time on Wednesday, NASA said.
Original file name: .CNI - Life on Mars.Reuter
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