Scientists have discovered how came the first oxygen on Earth

© Photo : Gerald Rgta the artist has imagined a hot spring, where 3.6-3.7 billion years ago could appear RNA-protein lifeScientists have discovered how came the first oxygen on Earth© Photo : Gerald Prins

. The proportion of oxygen in the Earth’s atmosphere remained extremely low after the appearance of the first photosynthetic microbes, for the reason that the rocks of the ancient continents were actively absorbed by its molecules, not allowing them to accumulate in the ocean and the air, according to a paper published in the journal Nature Geoscience.

«The saturation of the Earth’s atmosphere with oxygen could occur at any time. All it needed was the «right» chemical composition of the continents. We found that the chemical composition of the continents has changed dramatically just at the time when oxygen began to accumulate in the waters of the primary ocean of the planet,» says Mattijs Smith (Matthijs Smit) from the University of British Columbia in Vancouver (Canada).

Today scientists believe, the Earth in the distant past had reminded myself today in its atmosphere lacked oxygen and had a lot of carbon dioxide and methane. Its waters, resembling the temperature and consistency of boiling a thick soup, was inhabited by bizarre bacteria-the extremophiles, the traces of which in the form of deposits of a kind of «blankets» from colonies of microbes, scientists often find in the most ancient rocks of the Earth.

When exactly life began, yet no one knows – there is conflicting evidence that it existed already at 3.3-3.7 billion years ago or 4 billion years ago, almost immediately after the formation of the Earth and moon and the end of their «bombing» of large asteroids and comets brought the «blocks of life» on the Ground.

This life, as told by Smith that existed prior to the event, which geologists call «the great oxygen catastrophe.» About 2.4-2.32 billion years ago oxygen concentration in the atmosphere has increased dramatically, rising from 0.0001% to the modern 21%. The reason for its occurrence are considered to be the first photosynthesizing organisms, cyanobacteria, cleanse the atmosphere of CO2 and filled it with oxygen.

On the other hand, as scholars have noted, it remains unclear what exactly hindered the growth of the concentration of oxygen in the water and in the atmosphere of the Earth in the hundreds of millions of years, when cyanobacteria already existed in the primary ocean of the planet.

Some scientists suggest that the «extra» oxygen absorbed primary continental rocks of the Earth formed at the time when the oxygen in the atmosphere actually was not, and others believe that the role of «absorber» of oxygen assumed by the remains of living organisms that accumulated at the bottom of the oceans of the Earth hundreds of millions of years.

Smith and his colleague Klaus Mezger (Klaus Mezger) from the University of Bern (Switzerland) have found new evidence in favor of the first hypothesis by analyzing the chemical composition of tens of thousands of samples of bark, formed long before the «oxygen catastrophe» at a time when the proportion of oxygen in the atmosphere grew at the fastest rate.

For this analysis, the scientists used an ingenious technique – they measured the proportion of chromium and uranium in these rocks, different responds to the process of destruction of rocks with oxygen and water. Accordingly, the larger these differences, the longer and stronger the elements acted on these rocks, which allows to understand the role the world played in the emergence of its supply of oxygen.

As shown by these measurements, the proportion of chromium and oxygen in continental rocks began to change about three billion years ago that coincides with the emergence of the first photosynthetic organisms. About 300 million years before the «oxygen catastrophe», their ratio changes dramatically, indicating an equally dramatic change in one type of rocks to another, hardly absorbs oxygen. It is, as scientists believe, was the reason for the beginning of the «oxygen catastrophe», dramatically changed the face of the Earth and its first inhabitants and make it suitable for human existence and other living beings.

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