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Tuesday, Nov. 20, 2001

"The evidence that's been presented so far is less convincing than what I'd like," said Peter Buseck, an Arizona State University professor and co-author of a paper published Tuesday in the Proceedings of the National Academy of Sciences.

"Up until now, we have not gone out in print in this sort of way. We haven't tried to confirm their work, so we haven't had any conclusions that might cause some concern. That may happen after this paper appears," he said.

NASA researchers at the Johnson Space Center in Houston are aware of the work by Buseck and his colleagues but have not had a chance to study the new report, spokeswoman Eileen Hawley said.

The new evidence is based on observations of terrestrial bacteria using a specialized electron microscope coupled with a computerized program to control angles and positions precisely to generate accurate three-dimensional images.

The new technique gave researchers an unprecedented view of tiny crystals of a mineral called magnetite, which turned out not to be uniform in size or shape, as anticipated by the NASA team. One of the strongest claims by NASA researchers that the Mars meteorite holds evidence of ancient life was that magnetite crystals found in the rock were so structurally perfect, chemically pure and with such distinctive, three-dimensional shapes they could only have been produced by bacteria, rather than by an inorganic process.

The technology to accurately determine the size and shape of these crystals has only become available in the past few years and has not yet been used to study the magnetite deposits in the Mars meteorite. However, the research published Tuesday for the first time presents a detailed view of the terrestrial crystals, which turn out to be not quite as described by the Mars meteorite research team.

For starters, Buseck and his team show the shapes of bacterial magnetite grains vary more than scientists had previously thought. The shapes and sizes differ among bacterial strains and even within individual bacteria. That expanded variety makes it more likely bacterial and meteoritic magnetite grains could appear to match by simple chance.

The researchers also question the limited sampling presented by the Mars meteorite team offered as evidence of a direct match with terrestrial bacteria.

The NASA group selected only 27% of all the magnetite crystals present in the Martian meteorite for comparison with bacterial crystals.

Buseck said it is too early to know for sure the exact shapes of the meteor crystals, let alone whether they match identical crystals from bacteria on earth. The next phase of the research will be to make additional studies of magnetite crystals from the meteorite as well as several strains of terrestrial bacteria.

"We will look at them in far greater detail than others have been able to do before," Buseck said.

Copyright 2001 by United Press International. All rights reserved.