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rath
B.V. Info Seeker
Joined: Nov 26, 2003
Posts: 1530
Location: Australia
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 Posted: Thu Jul 03, 2008 4:40 pm Post subject: Aussie diamonds a clue to life birth |
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July 03, 2008
ANCIENT diamonds from the rugged rocks of Western Australia are about to trigger a modern scientific explosion.
Australian, Swiss and German researchers claim the rocks contain tantalising evidence that life began in Australia 4.2 billion years ago, just a geological blink after the formation of Earth 4.5 billion years ago.
Most experts agree that life was up and rolling 3.5 billion years ago. And a handful accept highly controversial evidence pushing life's birth back to 3.8billion-3.9 billion years.
So, as University of NSW astrobiologist Malcolm Walter said, "this will definitely throw the cat amongst the pigeons".
A team led by geochemist Alexander Nemchin, of the Curtin University of Technology in Perth, analysed 22 diamonds found inside zircon crystals that are three billion-4.25 billion years old. The zircons were discovered in the Jack Hills, east of Shark Bay.
The diamonds, technically "diamond-graphite inclusions", are only 70 microns wide, the thickness of a few human hairs. They probably formed under the pressure exerted by 100-150km of crustal rock above them.
Writing overnight in the journal Nature, Dr Nemchin's team claimed the diamonds contained two types, or isotopes, of carbon, C12 and C13. Significantly, there's more C12 than C13, and because this is the ratio produced by biological processes, such "light" carbon is used as a "signature" of life.
Predicting the debates their findings will produce, the team cautiously acknowledged that geochemical process may have produced the telltale "isotopic composition". "I myself am not convinced yet," Dr Nemchin said.
Geochemist Craig O'Neill, of Sydney's Macquarie University, agreed that geochemical processes could have created the light carbon. "But if it is the signature of life, that means life evolved and survived in one of the most hostile, violent environments we can imagine," he said.
Until about 3.8 billion to four billion years ago, Earth was bombarded by massive impacts, including one so enormous it knocked off a hunk of rock that became the moon.
Professor Walter suggested that if life did emerge 4.2 billion years ago, it either died out during the onslaught then restarted in quieter geological times, or, as Dr O'Neill suggested, it survived as "extremophiles", hardy microbes that survive intense heat, cold and pressure.
Bruce Runnegar - an astrobiologist with the University of California at Los Angeles and past director of NASA's Astrobiology Institute in Moffett Field, California - said the discovery of light carbon was a "spectacular analytical result" no matter how it was formed.
If it is eventually confirmed that the carbon was biogenic, that is good news for scientists who use it to search for early life. If it proves otherwise, they have got a problem. |
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The Great Escape a Good film 200 prisoners smuggled out of a camp the Germans said was escape-proof. the most daring breakout of World War2 a story of cunning & courage, Australian POWs figured prominently. In the real event no Americans were involved |
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