ORIGIN OF LIFE ON EARTH

Ten years ago, an international team of scientists reported evidence, in a controversial cover story in the journal Nature, that life on Earth began more than 3.8 billion years ago–400 million years earlier than previously thought. A UCLA professor who was not part of that team and two of the original authors will report in late July that the evidence is stronger than ever.

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The scientists see light carbon inclusions in a phosphate mineral called apatite, which is also the material of which bones and teeth are made.

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"This paper shows, with far greater confidence than we ever had before, that these rocks are older than 3.8 billion years," said Manning, who has conducted extensive research in Greenland. "We have shown that the rocks are appropriate for hosting life.

Manning agrees, saying he is confident the rocks contain evidence of ancient life, but "it’s not a slam dunk."

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An unanswered question is how life originally could have arisen from lifeless molecules and evolved into the already sophisticated isotope fractioning life forms recorded in the Akilia rocks.

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The research on the Akilia rocks is federally funded by the National Science Foundation (http://www.nsf.gov/) and the NASA Astrobiology Institute (http://nai.arc.nasa.gov/), a partnership between NASA, 12 major U.S. teams and six international consortia.

The carbon aggregates in the rocks have a ratio of about 100-to-one of 12C (the most common isotope form of carbon, containing six protons and six neutrons) to 13C (a rarer isotopic form of carbon, containing six protons and seven neutrons). The light carbon, 12C, is more than 3 per cent more abundant than scientists would expect to find if life were not present, and 3 percent is very significant, Harrison said.

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Carbon inclusions in the rocks were analyzed with UCLA’s high-resolution ion microprobe–an instrument.