New elements examined on the Martian ALH-84001 meteorite indicate that at one point life existed on the red planet, NASA said in a study to appear Tuesday the journal Proceedings of the National Academy of Sciences.
"The chains we discovered are of biological origin," said Imre Friedmann, a researcher at NASA's Ames Research Center in California.
Scientists observed magnetite crystals, an iron oxide, strung in chains like a "string of pearls," which they say are formed only by once-living organisms.
"Such a chain of magnets outside an organism would immediately collapse into a clump due to magnetic forces," Friedmann said.
The researchers said the chains, probably formed inside organic material, served as "compasses" for their host organisms and were preserved in the meteorite long after the organisms themselves decayed.
The scientists were able to see the tiny chains inside the 1.8-kilogram (four-pound) meteorite without destroying them using a special technique. Their flexibility and uniformity are further evidence they are of biological origin.
The meteorite was formed by a collision between an asteroid and the planet some 3.9 billion years ago, and was propelled toward Earth by another collision, the researchers said, around 13,000 years ago and discovered in 1984 in Antarctica.
"Until now, studying life has been like trying to draw a curve using only one data point -- life on Earth," Friedmann said. "Now we have two data points to draw life's curve."
A second research group from the US National Aeronautics and Space Administration has published a study to appear simultaneously in the same journal, highlighting the similarities between the Martian magnetite crystals and crystals formed inside magnetotactic bacteria present on Earth.
However, the researchers from NASA's Johnson Space Center in Houston, Texas, led by Kathie Thomas-Keprta compared the crystals but not the chains they formed.
The Ames study determined that the crystals were of similar size and shape, they did not touch each other and that the chains they formed were curved: additional signs, the researchers said, of a biological origin.
They also deduced from their great concentration in a small, two-kilo (4.5 pounds) meteorite that they must have been rather widespread on the surface of Mars.
And since Earthly bacteria that use magnetic forces require some oxygen, researchers said their presence on the meteorite denotes that 3.9 billion years ago there were plant-like organisms using photosynthesis on Mars.
In 1996, the Johnson Space Center team of researchers headed by David McKay first noted that the ALH-84001 meteorite contained mineral traces of biological origin, but their findings were seriously questioned by specialists in fissile bacteria – WASHINGTON (AFP)
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