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Precious little gems

Microdiamonds may hold signs of ancient life on Earth

11:58am, July 2, 2008

Ancient microdiamonds embedded inside ancient zircons found in western Australia suggest that life may have existed on Earth up to 4.25 billion years ago.

Chemical analyses indicate that the mini-gems contain higher-than-average concentrations of the carbon-12 isotope, researchers report in the July 3 Nature.

Experts strongly debate whether that anomaly is evidence that life existed on Earth so soon after the planet formed, 4.6 billion years ago. If true, however, the findings would put life’s earliest appearance at least 400 million years sooner than previously thought.

“If the light carbon signature is from life, then this is very big indeed,” says Craig O’Neill, a geoscientist at MacquarieUniversity in Sydney. “The trouble is, there are quite a few other mechanisms that can form light carbon signatures.”

Zircons, tiny crystals of zirconium silicate, are hard, du

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