By Sean Henahan, Access Excellence

ATHENS, Ga (August 12, 1996) At least one of the researchers who worked on the meteorite which researchers say may contain signs of microscopic life on Mars says he has no doubts that a crucial link in the chain of evidence is scientifically sound.

Graphic: False-color backscatter electron (BSE) image of fractured surface of a chip from ALH84001 meteorite showing distribution of the carbonate "globs."

"I feel very confident about it because we have several lines of evidence for the origin of the material," said Dr. Christopher Romanek, now of UGA's Savannah River Ecology Laboratory in Aiken, S.C. "Comparing the isotopic composition of the carbonate 'globs' to the surrounding matrix material clearly points to a low-temperature origin."

The evidence for low-temperature formation of the meteorite is vital to the theory that primitive microscopic life may have existed on Mars. The meteorite, known as Alan Hills 84001, was found in Antarctica some 13 years ago. It was formed on Mars 4.6 billion years ago and, according to the paper in Science, became covered with microorganisms between 3.6 billion and 4 billion years ago.

The researchers believe that about 16 million years ago, a comet or asteroid struck the Martian surface and blasted pieces of rock into space, where they drifted for millions of years. The meteorite, found in Antarctica, in 1984 fell to Earth about 13,000 years ago.

Romanek's involvement in the process occurred because of a chance encounter with the meteorite at the Johnson Space Center in Houston, where he was working on a two-year postdoctoral fellowship. His lab was near that of Lockheed-Martin researcher Dr. David Mittlefehldt, an expert on meteorites. Mittlefehldt had been working on the Alan Hills meteorite when he began to notice that it possessed some unusual characteristics.

"He had been working on meteorites called diogenites, but he realized that this particular meteorite had more in common with other known Martian meteorites," said Romanek. "So he sent some of the material to Dr. Bob Clayton, a preeminent isotope geochemist at the University of Chicago for oxygen isotpe analysis."

Clayton examined the rock and confirmed that it is consistent with a Martian origin. At that point, Mittlefehldt began to study the meteorite more in depth, using such techniques as electron-beam microprobe analysis. Realizing that the samples were truly unusual in nature, Mittlefehldt walked across the hall and asked Romanek if he would come take a look at what he was seeing.

Romanek became involved with the project almost immediately, looking at unusual carbonate spheroids or "globs," as they came to be called. He was able to separate some of them from the meteorite and began to analyze them using conventional techniques to look for stable isotope ratios. The spheroids, as it turned out, are composed of magnesium, iron and calcium, but they all contain carbon and oxygen as well, and Romanek specifically wanted to look at their isotopic signatures.

"What I found was that the samples were extremely enriched in carbon 13 compared to materials on Earth," said Romanek. "So it was clear it wasn't terrestrial; however the signature was nearly identical for the 'fingerprint' that has been proposed for the carbon dioxide of Mars. Using other models of the isotope record, I concluded that these spheroids must have formed between zero and 80 degrees Celsius."

Romanek then went to NASA scientist Everett Gibson and asked for an in-depth investigation of the meteorite. Gibson, in turn, took the evidence to NASA microscopy expert David McKay.

As the project accelerated in intensity, it changed its focus from being about geochemical processes to the search for evidence of life. In the meantime, Romanek wrote a paper about his findings which was published in a 1994 edition of issue of Nature (Volume 372, p. 655.)

"At this point, it was no longer an isotope problem but a microscope problem," said Romanek, who left NASA about two years ago to join the University of Georgia's Savannah River Ecology Laboratory. Still, he has stayed involved with the project, spending several weeks at a time at the Johnson Space Center in Houston. He has also talked nearly weekly on the phone with Gibson or Kathie Thomas-Keprta of Lockheed-Martin in Houston, also part of the team studying the meteorite.

Romanek says he had "eureka" moments when he realized the possible magnitude of the discovery: "Absolutely -- every time the team had a scanning electron microscope session. We were looking at this material at a resolution that not a lot of people have used before in this way. And we had to be so careful about what we were seeing. Were they artifacts that didn't originate on the rock? Were they dust grains? All of this had to be addressed in highly constrained experiments. This kind of checking is invaluable, but it takes a long time to do."

Related information on the Internet

Science Article: Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001, David S. McKay et al.

Life on Mars Report

More Mars Meteor Pictures

"Live From Mars"

NASA web site

Johnson Space Center

Informa tion on Shergotty-Nakhla-Chassigny (SNC) Meteorites

Clues to The Origins of Life