The study shows that the main role in this process was played not by microorganisms at all, but by continents.
It is known that during the first 2 billion years of our planet’s life, there was almost no free oxygen in the Earth’s atmosphere. And the time span between 2.4 billion and 400 million years ago represents an important chapter in the development of life on our planet, writes Forbes.
The researchers studied banded ironstone formations dated to this period and found that it was at this point that oxygen levels rose rapidly until they eventually reached the levels we see today. Note that the banded ironstone formations are fossilized microbial mats, which are mainly composed of silica and iron oxides, and contain the history of an important chapter in the life of the Earth.
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Up to this point, scientists had argued that oxygen levels rose as a result of the photosynthesis of the first microorganisms, which produced oxygen as a by-product, and then it was released into the Earth’s atmosphere.
However, a new study by a group of scientists from the University of Leeds now believes that this theory cannot actually explain what really happened. Examination of the banded formations of iron ore shows that oxygen did not build up gradually at all, rather it happened in bursts called oxidation events.
Scientists argue that at the time of the death of microorganisms, they were absorbed by other life forms, which means that oxygen would have to be absorbed from the atmosphere. As a result, atmospheric oxygen should have remained stable at low levels, but history shows that this was not the case.
The researchers claim that for a jump in oxygen in the atmosphere, the decay process had to be slowed down or even completely stopped. This probably happened due to the conservation of mineral-organic carbon. In simple terms, when minerals in the oceans, especially iron particles, bonded with dead organisms and prevented them from decaying and decaying.
Scientists have long known that mineral particles can bind to dead plants and algae, making them less susceptible to decay, said lead author of the study, professor of biogeochemistry Caroline Peacock. However, previously scientists have never tested how this could affect the amount of atmospheric oxygen. So he and his colleagues set about testing their theory.
A rough overview of the oxygen levels in the Earth’s atmosphere over time and various important events for Earth’s evolution and life
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Scientists have studied the period when the first continents on Earth were formed, which led to an increase in the land mass from which minerals, including iron particles, could be washed away by the wind into the ocean, for example.
It is known that the first land masses were formed on Earth about 3 billion years ago, when fragments of the primitive continental crust were grouped together to form the first continents. Over the next 500 million years, volcanic activity added land and plate tectonics, pushing the smaller continents into the first supercontinent.
In the course of the study, scientists found that the formation of the first supercontinent called Ur actually coincides with the first spike in atmospheric oxygen levels, which occurred about 2.5 billion years ago.
The lead author of the study, Dr. Mingyu Zhao, notes that the increase in mineral particles in the oceans should have reduced the rate of algae decomposition, and therefore had a significant impact on the growth of oxygen in the Earth’s atmosphere, and there is irrefutable evidence for this.
The researchers also found that smaller spikes in oxygen levels are associated with the formation of later supercontinents such as Columbia, Rodinia and Pangea.
Peacock hopes that the results of her and her colleagues’ work will provide a broader understanding of the conditions necessary for the development of complex life on other planets. At the very least, researchers now know that the presence of water is only one piece of the puzzle, but that’s not enough. Dry land is also an important part, which can act as a source of mineral particles that end up in the oceans.
Earlier, Focus wrote that the Earth is giving birth to a new ocean: scientists believe that it will divide Africa into two parts.
