New evidence of oxygen on ancient Earth

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Oxygen may have been present in Earth's ancient oceans, hundreds of millions of years before it began to mingle with the atmosphere.

MIT researchers say it's possible that oxygen was present in so-called oxygen oases in the oceans, long before what's described as the "Great Oxidation Event" some 2.3 billion years ago loosed the life-giving element into the Earth's atmosphere. Until then, oxygen molecules were rare and the planet was covered in a noxious mix of primordial gases.

If the theory holds up, it would mean that oxygen was present on Earth 300 million years before seeping in the atmosphere, creating ripe conditions for the development of life-nurturing marine environments.

The researchers conducted lab experiments which turned up evidence suggesting that aerobic organisms may have been able to survive on very low levels of oxygen in these undersea oases. Their findings were published in the Proceedings of the National Academy of Sciences.

"The time at which oxygen became an integral factor in cellular metabolism was a pivotal point in Earth history," Roger Summons, a professor of Geobiology at MIT and one of the report's co-authors, told MIT's news service. "The fact that you could have oxygen-dependent biosynthesis very early on in the Earth's history has significant implications."