Scientists, it seems, found a "trigger", which launched the development of complex forms of life on Earth
Scientists have long wondered how the atmosphere of our planet could be filled with oxygen. And it seems that two researchers, geologist Mattis Smith of the University of British Columbia and his colleague Klaus Mezger, found the answer in the continental rock, which is several billion years old.
"Oxygenation was just waiting for the right moment. Several factors were needed to make this happen, "says Smith.
In the atmosphere and oceans of the early Earth, free oxygen was absent, even though tiny cyanobacteria produced gas as a by-product of photosynthesis. Free oxygen is oxygen, not mixed with other chemical elements like carbon and nitrogen. For life in free oxygen, aerobic organisms are needed. About three billion years ago, there were changes when free oxygen began to accumulate in certain regions of the oceans. About 2.4 billion years ago, in just 200 million years, the oxygen level in the atmosphere unexpectedly increased 10,000 times. This period in the history of the Earth in science is called an oxygen disaster (or oxygen revolution), completely changing the chemical reactions taking place on the surface of our planet.
Smith and his colleague Klaus Mezger from the Department of Earth Sciences, the Oceans and the atmosphere of the University of Berne (Switzerland) are convinced that during this period there were also global continental changes. The scientists decided to find a connection between these events and engaged in a deep study of records on the geochemical composition of shale and igneous rocks around the world. In total, scientists have analyzed more than 48,000 different stones, whose age is several billion years.
"It turns out that at a time when free oxygen began to accumulate in the oceans, there were significant continental changes," says Smith.
Before the oxidation (oxygen disaster), the composition of the continents was rich in a rock with a high magnesium content and a low silica content, similar to that which can now be found in places like Iceland or the Faroe Islands. But more importantly, this is because this rock contained a mineral called olivine. When olivine comes in contact with water, it triggers chemical reactions that lead to oxygen blockage. This is most likely the case with oxygen, the production of which in the early history of the Earth was engaged in cyanobacteria.
But as the earth's crust continued to develop and move closer to the state that can be observed in her now, olivine eventually disappeared. Without this mineral, which triggers a reaction from interaction with water and consumes oxygen, the gas has finally been able to accumulate. As a result, the oceans were oversaturated and began to give it into the atmosphere.
"This, most likely, is the starting point for the appearance of the diversity of life that our planet is rich in. After these changes, the Earth became much more habitable and suitable for the development of complex forms of life. This required a trigger mechanism. And, it seems, we found it, "- comments Smith.
As for what could have caused such a significant change in the chemical composition of the continent, this question remains open for further research. Smith notes that modern plate tectonics began around the same time, and many scientists suggest that there is also some connection in this matter.
The findings of Smith and Mezger were published in the latest issue of the journal Nature Geoscience.
The article is based on materials .
Comments
Post a Comment