The collision of a planet the size of Mars, Thea, 4.5 billion years ago with Earth may have left traces in the depths of the latter.
According to scientists, this mixture is the ultra-low velocity zones located at the core of our native celestial body and the mantle – unusual structures in which seismic waves travel 50 percent slowly due to their density.
It is difficult to say for sure what these zones are, as they are about 2,900 miles [2,900 km] from the earth’s surface. One series of such formations is located below Africa and the other below the Pacific Ocean. The only source of information about the size, shape, and other characteristics of each is seismic data.
The authors of a paper published in the journal Nature Geoscience developed a computer model using the results of similar studies. The simulations showed that the above structures are not homogeneous, but are divided into layers of different composition. This indicates that during the many years of evolution of the celestial body, chemically diverse matter could not be completely mixed together.
According to scientists, the hypothetical history of the formation of ultra-low velocity zones begins more than 4 billion years ago, when the Earth was hit by a tee, which led to the formation of the moon (this is also part of the hypothesis). As a result, rocks, gases, and crystals would be dispersed in the vast ocean of magma, and heavy elements would sink to the bottom of the mantle. After them, relatively light substances followed the same path, which helped to form dense layers. Eventually, they would disintegrate into parts and be distributed in different places.
Of course, this does not explain the origin of each such zone. Researchers do not rule out that the reason for their emergence may be the penetration into the mantle of the oceanic crust, although the new hypothesis is not really far from logic.