Researchers say case for Mars bacteria unproved

WASHINGTON -- A group of researchers say NASA scientists have failed to prove their contention that a Mars meteorite contains evidence of ancient microbial life on the Red Planet.

A group led by Peter R. Buseck of Arizona State University said that the NASA researchers have inadequate evidence showing that tiny crystalline structures in Mars meteorite ALH84001 were formed by bacteria billions of years ago as the rock was sitting on the Martian surface.

A study appears today in the Proceedings of the National Academy of Sciences.

Buseck said that NASA-supported researchers claimed in February that crystals found in the meteorite are identical to crystals formed on Earth by bacteria. The material, known as magnetite, is formed by some bacteria that live on the bottom of lakes. The magnetic crystals act as a sort of compass to allow the bacteria to orient themselves as they move along the lake bottom.

'Much more uncertainty'

Buseck said there was inadequate similarity between Earthly magnetite and that found in the Mars meteorite to prove that the material was formed by a living organism.

"We find that there is much more uncertainty than they seem to believe," said Buseck, referring to the NASA researchers.

The Arizona State researcher said there are computer-driven electron microscope techniques that can be used to determine if the NASA researchers are correct. He said he plans to do such a study.

Everett Gibson, a NASA researcher who was among the group that first proposed that ALH840001 contained evidence of life, said that Buseck has not even looked at the Mars meteorite.

"How can he draw this conclusion without seeing the material?" Gibson asked. He said that other researchers have found evidence that supports the NASA group.

In 1996, Gibson and some other NASA-supported researchers announced that they had found evidence in ALH84001 of life -- microscopic fossils that could have been bacteria, and carbon chemicals that are linked to life processes.

They suggested that the bacteria lived on the Red Planet billions of years ago, when Mars had water and warmer temperatures, and that microbes left evidence inside the Mars rock.