Meteorite might show evidence of life on Mars

Posted: Wednesday, February 28, 2001

   Scientists have compelling new evidence that a meteorite from Mars might contain evidence of life, the discovery of a magnetic crystal that researchers say could have been made only by an ancient microbe.

   Findings published Tuesday in the Proceedings of the National Academy of Sciences bolster research that caused an uproar in 1996, when scientists, including a University of Georgia researcher, first suggested that crevices of the Mars meteorite found in the Antarctic might contain evidence of ancient microbial life.

   The lead author of Tuesday's paper said a chain of microscopic magnetic crystals found in the space rock, called Allen Hills 84001, or ALH84001, are similar to crystals formed on Earth by bacteria.

   ''I am convinced that this is supporting evidence for the presence of ancient life on Mars,'' said Kathie Thomas-Keprta, an astro-biologist at Johnson Space Center.

   Christopher Romanek, an assistant research scientist with UGA's Savannah River Ecology Lab, said the new research supports his team's 1996 findings of organic molecules in the same 4.6 billion-year-old meteorite, but he said more research must be done before scientists can link their evidence with theories about old life on the red planet.

   ''We haven't collected enough of it yet to make this claim that we found life on Mars, but it leads you on a path that may end in a conclusion there is or was life on Mars,'' said Romanek, who was a contributing author in Tuesday's Publications article.

   In 1994, Romanek was among the first to begin looking for signs of life in the potato-sized Martian meteorite. His brainstorm came after hearing a talk about bacteria entombed in terrestrial rocks. In recent years, the carbonate geo-chemist has focused on looking within the meteorite at the tiny magnetite crystals, small enough for one billion to fit on the head of a pin. He has also scoured scientific literature for inorganic explanations for the structures.

   Thomas-Keprta said there is no report of such magnetites being formed by any but biologic means. Because of the age of the meteorite, ''this is evidence of the oldest life form ever found,'' she said.

   The magnetic minerals serve as internal compasses within some bacteria, providing them a rudimentary sense of direction, and leaving behind a tell-tale chain pattern. One variety of the mineral found in ALH84001, Romanek said, forms a perfect match for magnetite made by bacteria found on Earth.

   Pleased that his earlier research seems to be ''holding up,'' Romanek said after five years of critiques from astro-biologists and the larger scientific community, he's taking a more conservative view of the research than most of his fellow researchers.

   ''For as many reasons as you can find for the biological argument you can find a greater number of scientists who say it doesn't have to be biological,'' he said. ''We're not the first people to look at a meteorite and say we found evidence for life.''

   Ralph P. Harvey, a geologist who has studied ALH84001, told reporters this week that the new conclusions are ''hasty'' and needs further study.

   The Associated Press contributed to this article.



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