It’s now established. Life existed in oceans at least 200 million years before oxygen appeared on Earth, a new study has revealed.
During this period in its history, known as Archaean, the Earth was covered by a poisonous smog of methane, ammonia and other toxic gases. So, life as we know it today could not have survived on the early planet.
Now, an international team, led by Rutgers University in New Jersey, has claimed that plant-like bacteria existed in the oceans for hundreds of millions of years while the Earth’s air was not fit to breathe.
In fact, the findings are based on analysis of ancient preserved seabed rocks from South Africa dating back some 2 to 3 billion years — the study found chemical evidence of nitrogen cycles which could not have taken place without the presence of free oxygen, The Daily Telegraph reported.
Nitrogen cycles relate to the way living things obtain and use nitrogen to produce complex organic molecules.
Evidence of nitrogen cycles provides a “fingerprint” of life.
According to the scientists, organisms which produced oxygen as a by-product of photosynthesis must have evolved by around 2.5 billion years ago. Oxygen did not begin to enrich the atmosphere until at least 200 million years later.
“Nitrogen is a relatively inert molecule and has an atmospheric lifetime of the order of around one billion years.
In contrast, oxygen... is highly reactive and must be produced continuously by oxygenic photosynthesis.
“It is unlikely that the gas was present above trace levels in the atmosphere of the Earth during the first two billion years of the planet’s history, but when oxygenic photosynthesis first arose on the Earth is not known with certainty,” the scientists said.
The findings have been published in the latest edition of the Nature Geoscience journal.
