Previous to the presence of oxygen, methane and ammonia were the main ingredients of the atmosphere. Currently, nitrogen makes up about 78% of the Earth’s atmosphere, followed by oxygen at 21%, argon at less than 1%, carbon dioxide at about 0.04%, and trace amounts of other gases and water vapor.

The result of the researchers’ work was found in the Friday, September 28, 2007 issue of Science. The team was headed by earth and space exploration professor Ariel Anbar, Arizona State University, and geochemistry professor Alan Jay, University of Maryland.

Anbar commented on the discovery, “We seem to have captured a piece of time before the Great Oxidation Event during which the amount of oxygen was actually changing – caught in the act, as it were.”

Further information about the study appears at in the article “Researchers detect hint of oxygen 50 to 100 million years earlier than first believed” at http://www.eurekalert.org/pub_releases/2007-09/asu-rdh092007.php.

Scientists wish to know more about these time periods in Earth’s distant past so they can explain why life-giving oxygen suddenly became more prevalent in the Earth’s atmosphere and to learn more about how Earth evolved over billions of years of time. Examination of the Earth shows scientists that our planet is about 4.56 billion years old.


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