Friday, August 24, 2012
The diamonds and the Origin of Life
Small pieces of diamond fake an embryonic Earth may contain the oldest traces of life, according to a study. The analysis showed that the crystals contain a type of carbon often associated with plants and bacteria. The rare gems were found inside zircon crystals, formed a few hundred million years after the Earth formed. In an article published in the journal Nature the researchers caution that the results are not definitive proof of early life forms, but "do not exclude" the possibility.
"We are all a little skeptical," said Dr. Martin Whitehouse of the Natural History Museum of Sweden, one of the authors of the research. If coal was derived from primitive organisms, would set back the date of the appearance of life about 500 million years ago to more than 4,250 million years. The Earth is 4600 million years.
Small crystals of zircon-of just 0.3 mm, were found in the Jack Hills of Western Australia. Residues are ancient rocks that have long since disappeared. "We have no rocks. These zircons are only small fragments of something that was broken, healed and was redeposit as sediments," explained Dr. Whitehouse. Data radioactive suggested that some of the crystals formed to 4,400 million years ago.
Scientists describe this phase in Earth history as the Hadean and long thought to be impossible for life has been initiated at this time, due to the inhospitable conditions on the young planet. But Jack Hills zircons have begun to cast doubt on this theory.
Scientists analyzed 22 graphite and diamond inclusions in 18 zircon crystals. Small zircon crystals were found in the Jack Hills of Western Australia. The results showed that the capsules containing unusual levels of a mild form or isotope of carbon, known as carbon 12.
"The most common way to form light carbon in modern Earth is photosynthesis," said Dr. Alexander Nemchin of Curtin University of Technology, Australia, another author of the paper. During this process preferably lightweight bodies coal extract, leaving the heavier forms in the atmosphere.
"When they die, they preserve that signature," he said. The results of the experiments show team carbon inclusions have a variety of isotopes, as noted; suggest that the coal reserves were "heterogeneous". This would have to be buried deep in the earth to generate extreme pressures necessary to become diamonds.
"If this material was life-which presumably would have formed on the surface-a process then you need to take down some 150 km or 200 miles," said Dr. Whitehouse. However, the team admitted that their conclusions are not definitive.
Currently, it is believed to be the oldest example of life-signs dating back 3,700 million years, was discovered by Professor Rosing in an area of deformed rocks in West Greenland called Isua Belt. There also remains chemicals suggest the presence of photosynthetic life form. But are crucially makes a complete sequence of rocks, rather than single crystals.
Tempt hesitant but
"When you look at the carbon isotopes, could be interpreted as biogenic because we know that the biological process itself generates light carbon isotopes. Yet, of course there are other processes that can do that," said Dr. Whitehouse to the BBC.
Other possibilities include chemical reactions involving carbon oxides or material brought from space by meteorites. However, some observers have raised the possibility that diamonds have been contaminated while polishing the zircons. "If you look at the photos show, is always that these diamonds are of cracks, fissures and cavities," he told BBC Professor Minik Rosing.
If extraneous original features noted, one would expect at least some were embedded in the crystal structure. "There is always the fear that they may not actually be primary." However, Rosing said that the possibility that the markings were signs of very early life was "tempting".
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