HTTP:: Earth 039 s Oxidation Tracked with Chromium Isotopes
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One of the basic facts of life is clearly the knowledge that life on our planet cannot survive without oxygen. When the Earth first formed, there was a very small concentration of the gas, maybe less than one percent of the total atmosphere. However, two big oxidation events were recorded over the eons, both of which eventually determined the appearance of complex life. Now, new studies of these events, conducted based on chromium-isotope analysis, reveal more puzzling questions about the early days. The Great Oxidation Event (GOE) was the first instance in which the oxygen concentration in our planet's atmosphere increased noticeably since the Earth solidified from a ball of hot magma. Until now, experts believed that it took place some 2.45 to 2.2 billion years ago, based on evidence collected from analyzing molybdenum and rhenium isotopes, among isotopes of other metals. The second steep rise was estimated to have taken place some 750 million years ago, when the condit!
ions again became appropriate for the development of more complex organisms. By analyzing samples of banded iron formations â€" an iron-rich sedimentary rock â€" dating from around and in between the two main periods of intense oxygen increases, experts from the University of Copenhagen, in Denmark, led by researcher Rob...
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http://news.softpedia.com/news/Earth-039-s-Oxidation-Tracked-with-Chromium-Isotopes-121339.shtml
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