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Last updated on April 17, 2014 at 12:01 EDT

Latest Hiroshi Ohmoto Stories

2009-04-17 11:14:53

Sedimentary rocks created more than 2.4 billion years ago sometimes have an unusual sulfur isotope composition thought to be caused by the action of ultra violet light on volcanically produced sulfur dioxide in an oxygen poor atmosphere. Now a team of geochemists can show an alternative origin for this isotopic composition that may point to an early, oxygen-rich atmosphere."The significance of this finding is that an abnormal isotope fractionation (of sulfur) may not be linked to the...

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2009-03-25 08:14:02

Red jasper cored from layers 3.46 billion years old suggests that not only did the oceans contain abundant oxygen then, but that the atmosphere was as oxygen rich as it is today, according to geologists. This jasper or hematite-rich chert formed in ways similar to the way this rock forms around hydrothermal vents in the deep oceans today. "Many people have assumed that the hematite in ancient rocks formed by the oxidation of siderite in the modern atmosphere," said Hiroshi Ohmoto, professor...

2006-08-23 18:25:00

LONDON (Reuters) - Scientists may have to rethink accepted theories of how the prehistoric earth's atmosphere developed after new discoveries in ancient sulphur raised serious questions, researchers said on Wednesday. Up to now it has been generally accepted that the earth's atmosphere was devoid of oxygen for some 80 percent of its existence. "The popular model is that there was little oxygen in the earth's atmosphere before about 2.4 billion years ago," said Hiroshi Ohmoto of Pennsylvania...

2006-08-23 18:25:00

LONDON -- Scientists may have to rethink accepted theories of how the prehistoric earth's atmosphere developed after new discoveries in ancient sulphur raised serious questions, researchers said on Wednesday. Up to now it has been generally accepted that the earth's atmosphere was devoid of oxygen for some 80 percent of its existence. "The popular model is that there was little oxygen in the earth's atmosphere before about 2.4 billion years ago," said Hiroshi Ohmoto of Pennsylvania State...