A University of Washington
press release by Hannah Hickey dated Feb 16 2015
discusses a
paper published in Nature that raises the possibility that
life on Earth may have appeared much earlier than generally thought.
Quote:
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Originally Posted by Hannah Hickey, University of Washington
The authors analyzed 52 samples ranging in age from 2.75 to 3.2 billion years old, collected in South Africa and northwestern Australia. These are some of the oldest and best-preserved rocks on the planet. The rocks were formed from sediment deposited on continental margins, so are free of chemical irregularities that would occur near a subsea volcano. They also formed before the atmosphere gained oxygen, roughly 2.3 to 2.4 billion years ago, and so preserve chemical clues that have disappeared in modern rocks.
Even the oldest samples, 3.2 billion years old – three-quarters of the way back to the birth of the planet – showed chemical evidence that life was pulling nitrogen out of the air. The ratio of heavier to lighter nitrogen atoms fits the pattern of nitrogen-fixing enzymes contained in single-celled organisms, and does not match any chemical reactions that occur in the absence of life.
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Press release here -
http://www.washington.edu/news/2015/...ion-years-ago/
Paper here in
Nature provided under their recent "content sharing initiative"
entitled "Isotopic evidence for biological nitrogen fixation by molybdenum-nitrogenase from 3.2 Gyr" -
http://www.nature.com/articles/natur...O4KeZUw8TprrnH