Monday, April 26, 2004

It Came From Beneath the Geek

New evidence that life emerged early on Earth has come from an international group of geologists studying rocks in South Africa, the Beeb for April 22 tells us.

The evidence consists of microscopic tubes - averaging just 4 micrometers across and 50 micrometers long (i.e., 4x50 millionths of a meter) - found in volcanic glass dating from 3.5 billion years ago. They were caused, the researchers say, by microbes eating their way into rocks that formed as lava oozed out and cooled.

Recently-made microtubules have been discovered previously and the idea that they were caused by rock-eating microorganisms is shown by the fact that the tubules contain nucleic acids and elevated levels of carbon and nitrogen. The tubules in this case also contain carbon, which the researchers say is organic, noting that the surrounding volcanic rock contains very little carbon.

Key to the discovery is the fact that the fine structure of the tubules show that they were overgrown by a metamorphic mineral called chlorite, the result of volcanic glass being subjected to pressure and thus heat. What that showed is that the tubules are much older than the chlorite and thus could not have been made "recently" in geologic terms.

The discovery adds weight to the belief that life on Earth emerged as long as 3.7 billion years ago.

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