Raman spectroscopy could turn the history of the early Earth upside down and hint that conditions were suitable for life as little as 250 million years after its formation, pushing back the so-called Hadean era several hundred million years.
Alexander Nemchin, Robert Pidgeon, and Simon Wilde of Western Australia's Curtin University of Technology together with Martina Menneken and Thorsten Geisler-Wierwille of the Mineralogical Institute at Westf?lische Wilhelms University of M?nster, Germany have used the technique to probe a thousand ancient zircon crystals from the Jack Hills region of Western Australia.
Zircon crystals are tough and relatively resistant to being melted, thereby retaining vital clues about past events occurring in the Earth's crust and mantle. However, even these tough crystals should not have survived the very earliest geological phase - the Hadean era - during which the earth's surface was a seething mass of lava and was continuously bombarded by meteorites and comets from space.
Recent studies of these ancient crystals hinted that the Earth may have cooled much more quickly than previously thought, suggesting that a continental crust and oceans formed as early as 4.4 billion years ago.
Menneken and her colleagues examined tiny diamond inclusions within the Jack Hills zircons using confocal micro-Raman spectroscopy to obtain structural and chemical information and used uranium and lead isotope dating to reveal that these ancient chunks of carbon are well over four billion years old. That is almost one billion years older than the previous record for terrestrial diamonds. Moreover, they believe that these diamonds crystallized within 300 million years of the formation of the Earth itself.
The authors examine possible scenarios in which the diamonds might have formed and conclude that the crystals most closely resemble those found in ultrahigh-pressure conditions. They suggest that these findings imply a relatively thick continental crust and crust-mantle interaction at least 4.25 billion years ago.
http://www.spectroscopynow.com/coi/cda/ ... d=6&page=1
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