UH challenges
Mars life theory

Isle scientists cast doubt
on NASA's conclusions

By Helen Altonn
Star-Bulletin

An ancient meteorite found in Antarctica that NASA scientists claim contains evidence of life on Mars more likely is a "shocked rock," University of Hawaii scientists say.

Casting a shadow on the idea that the meteorite harbored fossils of Martian life are planetary scientists Edward Scott, Akira Yamaguchi and Sasha Krot.

They say their research indicates the carbonates and minerals weren't formed by organisms but were melted by shock waves from a powerful impact about 4 billion years ago.

"We're not saying there's no life on Mars, just that the evidence probably was misinterpreted," said Scott, who works on meteorites in the Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology.

David McKay and associates at the NASA Johnson Space Center last August shook the world with an announcement that a 16-million-year-old piece of meteorite might have remains of ancient Martian bacteria.

The rock, known as ALH84001, has been the subject of international study and debate.

Those who believe the rock contains ancient fossils argue that carbonates inside the rock formed at moderate temperatures over long periods of time and mineral-rich water in tiny cracks made a good environment for bacteria.

Others say the carbonate molecules were formed in a hot flash, such as from a meteorite impact.

When a comet or asteroid hits a planet, Scott said, it makes big craters that create shock waves that travel into the ground, compressing, melting and fracturing the target rock. "Everyone agrees this martian meteorite was involved in a big impact," he said.

His team got a section of the meteorite ALH84001 after the NASA scientists announced their discovery. "The people who studied it didn't do all the studies we would want," he said.

His group also studied a number of shock meteorites, he said. "We wanted to look at sections to see whether carbonate was present when shocked and how it responded if it was present."

He said ALH84001 was part of target material on Mars when a big impact occurred millions of years ago.

It probably moved the meteorite from its location in the martian crust and heated the rock enough to record the time of the event, he said. "The shock wave from the impact melted the plagioclase (silicate mineral), into glass," Scott said.

"We infer that the carbonate was also melted and squirted into the fracture."

Findings of the University of Hawaii scientists appear in the current issue of the journal Nature.

Scott said reviewers initially had a lot of objections, but his group answered them. Although many still had reservations, they felt the findings were strong enough for publication, he said.

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Reuters contributed to this report