Agence France Press in Washington and other news agencies released the information on February 27, 2001, that elements taken from the Martian ALH-84001 meteorite indicate that there was life on Mars billions of years ago. The findings of the international team of scientists were published Tuesday in the Proceedings of the National Academy of Sciences periodical.
Scientists such as Imre Friedmann, a researcher at NASA's Ames Research Center in California, have observed magnetite crystals, an iron oxide, strung in chains like a "string of pearls," which they investigated and found that they can only be formed by living organisms.
"The chains we discovered are of biological origin. Such a chain of magnets outside an organism would immediately collapse into a clump due to magnetic forces."
The researchers said the chains, probably formed inside organic material, were preserved, fossilized in the meteorite long after the organisms themselves decayed.
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 around 13,000 years ago, the researchers said. It was discovered in Antarctica in 1984.
When NASA announced in 1996, that a team of researchers led by David McKay and working at the US National Aeronautics and Space Administration's Johnson Space Center in Houston, Texas, noted that it contained mineral traces of biological origin, their findings were met with harsh skepticism, in the scientific community, and were subsequently called into question by some scientists. Later, the evidences just added up.
Meanwhile, the international list of researchers jumping on the Allen Hills meteorite bandwagon has grown large. Seventeen researchers were involved in three papers made public yesterday. Much of the research into the rock has been funded by the National Science Foundation, the Smithsonian Institution and NASA's Astrobiology Institute.
The study highlights the similarities between the Martian magnetite crystals and crystals formed inside magnetotactic bacteria present on Earth. The Ames study determined that the crystals were of similar size and shape, that they did not touch each other and that the chains they formed were curved, additional signs of a biological origin.
They also deduced from their great concentration in a small, two-kilogram (4.5-pound) meteorite that they must have been rather widespread on the surface of Mars. And since bacteria on Earth that use magnetic forces require some oxygen, researchers said their presence on the meteorite denotes that there were plant-like organisms using photosynthesis on Mars 3.9 billion years ago.
The very next day already, other scientists had already claimed in response that...
"The scientists studying the Mars rock haven't really eliminated the possibility that these structures are inorganic in origin."
The study has shown that there is currently no known inorganic chemical means of producing these magnetite crystals with their unique morphologies.
Kathie Thomas-Keprta, lead author of one of the new papers, responded that the researchers have taken a more in-depth look at the structure of the magnetites and have done an extensive literature search for other studies that might show analogous structures created by inorganic means, and zero were found.
But the bottom-line is, as Thomas-Kperta said, that the detail of the team's original paper, published in the December issue of Geochimica et Cosmochimica Acta, was voluminous and may not have been read widely or thoroughly by critics.
"These shapes and features and properties that we found in the Allen Hills magnetite have been understood for years to indicate biogenic origin," NASA geologist David McKay said today.
No one has succeeded in producing similar structures via inorganic means, despite serious efforts such as the project going on at the Johnson Space Center, where McKay and Thomas-Kperta work.
"At some point you have to ... accept that the only way they could be produced is by biology," McKay said.
Research will continue. McKay expects proof of life on Mars to come within five years, based on study of a dozen or so Mars rocks found on Earth.
"We're not expecting any one paper or any one line of evidence to convince people," McKay said. "But we think that over a period of time ... people will be convinced by the evidence, not by us, not by claims in the press."
Meanwhile, more rocks from Mars have been studied by the same researchers who originally examined the Allen Hills meteorite. Two meteorites, called Nakhla and Shergotty, showed the same evidence of microfossils and other remnants of early life as Allen Hills, according to a team of researchers led by Everett Gibson, a geochemist at JSC.
The next big step to take for the scientific community is to accept the new conclusions from the recent reevaluation of the Viking LR experiment and acknowledge that there is still life on Mars nowadays.
