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Meteor study pours cold water on warm Mars theory

Posted on: Thursday, 21 July 2005, 18:02 CDT

WASHINGTON (Reuters) - A study of meteorites chipped off the surface of Mars suggests the planet has been frozen for 4 billion years and probably never had the warm wet conditions that could have given rise to life, two researchers said on Thursday.

Their study of two meteorites that fell to Earth suggests they were never in warm conditions. The report, published in the journal Science, contradicts theories the now-frozen planet may once have been warm enough for life to have arisen.

"First, we evaluated what the meteorites could have experienced during ejection from Mars, 11 to 15 million years ago, in order to set an upper limit on the temperatures in a worst-case scenario for shock-heating," said Benjamin Weiss, an assistant professor at the Massachusetts Institute of Technology. He did the work while a graduate student at the California Institute of Technology.

They concluded the two meteorites were unlikely to have been above the boiling point of water during their ejection from the martian surface 11 million years ago.

Then Weiss and fellow student David Shuster measured the amount of argon remaining in the samples.

Argon, a gas, is known to leak out of rocks at a rate that depends on temperature.

The cooler the rock has been, the more argon will have been retained.

"The small amount of argon loss that has apparently taken place in these meteorites is remarkable. Any way we look at it, these rocks have been cold for a very long time," Shuster said in a statement.

Their calculations suggest the Martian surface has been frozen for most of the past 4 billion years.

"On Earth, you couldn't find a single rock that has been below even room temperature for that long," Shuster said.

That does not mean that rovers looking for evidence of warm springs, lakes or seeps on Mars are wasting their time. Geothermal activity below the surface could have created small areas that could harbor life.

"Our research doesn't mean that there weren't pockets of isolated water in geothermal springs for long periods of time, but suggests instead that there haven't been large areas of free-standing water for 4 billion years," Shuster said.

"Our results seem to imply that surface features indicating the presence and flow of liquid water formed over relatively short time periods," Shuster said.

Source: REUTERS

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