Scientists: Life Once Existed on Mars
W A S H I N G T O N, Feb. 27 -- A controversial finding that a meteorite fromMars might contain evidence of life has been boosted by thediscovery of a magnetic crystal that researchers say could havebeen made only by a microbe.
In a study appearing today in the Proceedings of the NationalAcademy of Sciences, researchers at the Johnson Space Center inHouston say a crystalized magnetic mineral called magnetite, foundin a Martian meteorite, is similar to crystals formed on Earth bybacteria.
"I am convinced that this is supporting evidence for thepresence of ancient life on Mars," said Kathie Thomas-Keprta, anastrobiologist at the space center and the first author of thestudy.
Thomas-Keprta said there is no report of such magnetites beingformed by any but biologic means.
The magnetite crystal was found in a Mars meteorite called AllenHills 84001, or ALH84001. Researchers at the Johnson Space Centerin 1996 announced that the space rock contained microscopicevidence of life, but their claim has been dismissed by most otherresearchers.
Life Might Still Exist
Thomas-Keprta said the new study strongly supports the originalclaim and may even suggest that there is still microscopic life onMars.
"If it existed there at one time, we would expect it to existtoday," she said.
The new finding is supported by a second paper in Proceedings.
E. Imre Friedmann, a biologist at NASA's Ames Research Center inMoffett Field, Calif., said an electron microscope examination ofALH84001 had found evidence of magnetite crystals formed in chains.
Friedmann said that on Earth the bacteria that make magnetiteforms the material in chains and that these chains are surroundedby a membrane. Under the electron microscope, fossilized images ofboth the chains and the membrane can be seen, he said.
"We see chains that could have been formed only biologically,"said Friedmann. "There is no way you could come up with anon-biological explanation."
On Earth, some bacteria that live on the bottom of lakes producemagnetite as a navigation aide. The magnetic crystals act as a sortof compass to allow the bacteria to orient themselves as they movealong the lake bottom.
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