Sunday, September 30, 2007

Scientists push back origins of Earth's oxygen (Reuters)

I just read an article about scientists pushing back origins of Earth's oxygen.

Did the oxygen actually begin to rise about 2.5 billion years ago? The scientists are finding some evidence from some rocks that the activity occured 50 to 100 million years before the Oxygen Catastrophe (known as the Great Oxidation Event).

For about the first half of the planet's existence, the environment had nearly no oxygen. I am curious to know how the planet acquire the oxygen after the atmosphere started to become thicker. Did part of oxygen get trapped inside the planet during its birth?

Like living things, oxygen and other gases have evolved for billions of years.


Jacob Haqq-Misra said...

During the first part of Earth's history (the Hadean and Archean), the atmosphere actually may have been thicker than now to compensate for the faint young Sun. This oxygen-free atmosphere could reasonably have had a significant methane constituent, as methanogens were a likely extant form of life.

Oxygenic photosynthesis probably did evolve before the rise of oxygen; once oxygen started to become a notable atmospheric constituent, though, the form of Earth's biota changed significantly. Methanogens had been a dominant life form on the planet, but they (and many/most organisms) could not survive in an oxic environment--today, methanogens live in suitable anoxic environments (such as rice paddies and cow's stomachs). The success of cyanobaceria, then, led to the increase of atmospheric O2 (which would disappear in the absence of life) and the oxydation catastrophe that caused a vast majority of species to adapt or perish.

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