The bowels of the Earth in the first era of her life was far hotter.
The Earth started to exchange gases and liquids with the atmosphere and hydrosphere unexpectedly later, about 2.5 billion years ago. It tells the extraordinary nature of cooling the planet, say geologists in an article published in the journal Nature.
“Most people are unaware that in the bowels of the Earth there is a huge amount of water, various gases and other volatile substances. Their share is relatively low, but it kompensiruet the huge mass of the mantle. For this reason, the “breathing” of the planet, the exchange of gases between the lithosphere, atmosphere and hydrosphere plays an important role in the existence and evolution of life,” says Rita Parai (Rita Parai) from Washington University in St. Louis (USA).
According to geologists, life exists on Earth and absent on Venus because our planet is not standing still and are constantly “migrate” between the surface and deep layers of the lithosphere. The movement of continents, the gradual immersion of their breeds in the depths of the mantle, and their subsequent “ascent” help the Earth “dump” the excess heat and to stabilize the climate.
This process, as scientists believe, not only affects the climate, but also on the composition of the atmosphere and oceans of the Earth. When the rocks of the continents sink into the mantle they carry with them large quantities of sediment containing various gases, water and other volatile substances. They return to the surface with eruptions that often dramatically changes the composition of air and water, and greatly affects life on earth.
For example, recently geologists have discovered that the “ascent” of the mantle in the area around Norilsk has led to the saturation of the atmosphere large amounts of greenhouse gases and “seeding” the oceans with nutrients, accelerating microbial growth. Both of these events occurred in approximately 255 million years ago, was the “trigger” for the Permian extinction, the most serious disaster in the history of life on Earth.
Pari and her colleague Sujoy Mukhopadhyay (Sujoy Mukhopadhyay) from the University of California, Davis (USA) have discovered, when you start such “lungs” of the planet, studying ancient rock samples of the crust and mantle of the Earth.
As explained by geologists, the bowels of the earth contain small quantities of noble gases, falling back as with the “sinking” of the bark, and the resulting decay of uranium, thorium and other radioactive elements.
Mukhopadhyay and Pari noticed that the proportion of isotopes of one of these gases, xenon, will be very different for breeds that are frequently exposed to water and the atmosphere, and primal matter of the Earth. For example, the primary mantle needs to contain a relatively large amount of xenon-129 and xenon-136, and the air and reworked the rocks of the crust — xenon-124 and xenon-128.
Following this idea, the researchers analyzed several samples of meteorites, similar in composition to the primary matter of the Earth and rocks from the mantle, leaving the bowels of the planet relatively recently, and tried to calculate the time of the launch of its “lungs”.
These calculations showed that the “atmospheric” xenon is almost completely absent in the bowels of the Earth during the first two billion years of life on the planet. These findings were a surprise to scientists.
On the one hand, it could mean that the tectonic processes and the cycle of rocks in the lithosphere suddenly start later, only 2.5 billion years ago. This, according to Pari, it is highly doubtful, given the existing geological evidence. On the other hand, scientists do not exclude the possibility that xenon and other gases just did not get into the gown for the reason that the bowels of the Earth in the first era of her life was far hotter than we believe today.
This led to the fact that most of the gases leaving the rocks of the crust before they have time to sink into the deeper layers of the mantle, which prevented atmospheric xenon “to mix” with underground reserves of gas and change their isotopic composition. About 2.5-2.4 million years ago, they cooled dramatically, the cause of which remains to be seen.
Regardless of which of the theories will be true, and that another interpretation of this discovery significantly change our picture of the shape of the early Earth and the conditions in which appeared the first living organisms, the authors conclude the article.
