Scientists: Life Once Existed on Mars

W A S H I N G T O N, Feb. 27, 2001 -- 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.

Friedmann said the bacteria require an environment that is lowin oxygen. The built-in compass "helps them navigate in the properoxygen levels," he said.

Thomas-Keprta said the magnetite is "a bacteria fossil, sort oflike dinosaur bones."

She said magnetite could not come from Earth organisms becauseit was encased inside the meteorite in a carbonate mineral that hasbeen age-dated at 3.9 billion years old.

Other Scientists Not Convinced

Because of this age, said Thomas-Keprta, "this is evidence ofthe oldest life form ever found."

Mars now has neither standing water nor a magnetic field, whichwould prompt bacteria to make magnetite. But experts believe thatthe planet once had oceans, an atmosphere and a magnetic field.Thomas-Keprta said it was during this period, billions of yearsago, that the bacteria lived and made the magnetite found inALH84001.

Some researchers who rejected the 1996 study by the JohnsonSpace Center scientists said they are not convinced by the newevidence.

Ralph P. Harvey, a geologist who has studied ALH84001, said thenew conclusions are "hasty" and should not be accepted withoutfurther study.

"I don't think this report should be considered as proof" thatlife ever existed on Mars, said Harvey, but he did not totallyreject the Thomas-Keprta interpretation.

"The door is still open until further evidence is rolled out,"said Harvey.

He said he is troubled that Thomas-Keprta and her co-authorsfound many crystals of magnetite in the meteorite, but arereporting only on those crystals that they believe could have comefrom bacteria.

"All of the rest of the magnetites say 'No' to life," saidHarvey. "They are focusing only a minority of magnetites in thisrock."

Also, said Harvey, the researchers are concluding that theselected crystals could be formed only by a life process when thereis little research to support this.

"Their support for these magnetite crystals is that they havenever been found in a non-biological setting," he said. "It is inmy mind hasty to rule out another origin."

At 4.6 billion years, ALH84001 is the oldest of 16 meteoritesfound on Earth and identified chemically as originating from Mars.Scientists believe that an asteroid smashed into Mars 13 million to16 million years ago and catapulted the Martian chunk into orbit.It wandered in space for millions of years and finally fell toEarth about 13,000 years ago. It was found on the Allen Hills icefield in Antarctica in 1984 and has been intensely studied since.