Martian meteorite shows signs of life

29 Nov 2009, 2:14 pm   -   Source: New Scientist
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A meteorite from Mars could contain signs of prehistoric life, say scientists. (Getty)

A meteorite from Mars could contain signs of prehistoric life, say scientists. (Getty)

Controversial theories that a meteorite thought to have contained signs of life on Mars have been revisited by a new analysis.

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It's arguably the most scrutinised piece of rock ever. Now an even closer look at a meteorite from Mars suggests it may show signs of life after all.

In 1996, David McKay of NASA's Johnson Space Center in Houston, Texas, and colleagues proposed that a chunk of Mars rock found in Antarctica, called ALH 84001, contained possible signs of past life on the Red Planet, such as complex carbon-based molecules and microscopic objects shaped like bacteria.

Many researchers doubt the claim, however, and various suggestions have been made for how the structures could have been created without life.

One area of disagreement centred around nanocrystal magnetites in the rock, some of which appear to have chemical and physical features identical to those produced by contemporary bacteria. Sceptics of the biological explanation suggested that the magnetites were created when carbonate decomposed under high pressures and temperatures, perhaps in the heat of the impact that ejected the meteorite 15 million years ago or deep beneath the Martian surface.

Now a fresh analysis by McKay and colleagues rules out the carbonate decomposition explanation.

The researchers have used high-resolution electron microscopy not available 13 years ago to study the physical and chemical make-up of the magnetites in detail, and found that no plausible geological scenario could explain the carbonate decomposition origin.

Dennis Bazylinski at the University of Nevada in Las Vegas told British newspaper The Times: "Until now I was on the fence, but this paper has really thrown out the non-biological explanation."

The possibility that the rock contains fossilised microbes received another boost in August when a team led by Paul Niles, also of NASA Johnson, showed that carbon in the meteorite was deposited in balmy water conducive to life, rather than a scorching temperature above 150 °C as had been proposed previously.


 

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Your Comments

NASA and life

Stuart - from Canberra, 3 years ago

As far back as the 60's various organisations around the world, including NASA became intimately aware of intelligent life on bodies within and outside our solar system. The information, interviews with the scientists involved, and evidence to suport this is widely available to those who look. These articles on past microbial life are window dressing to the disinformed.

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