By Chris Skeldon 
In the 1980s, geophysicists made an amazing discovery: two giant blobs of unusual materials had been found deep within the Earth, one under the African continent and the other under the Pacific Ocean.
Each bubble is twice the size of the Moon, and research conducted in the past decade has revealed that it is composed of different elements than those that make up the Earth’s mantle.
This week, scientists proposed a new theory that could solve the mystery of what these bubbles in the Earth’s mantle are.
The current theory about the origin of the Moon is that it was the result of the collision of a forming planet with a still-forming Earth, 4.5 billion years ago.
Earth’s collision with Theia, a Mars-sized protoplanet, would have released enough material into space to clump together to form the Moon.
Theia’s “remains” remained to be found, but there were no traces, and nothing was ever found in the asteroid belt or any meteorite.
The answer does not lie in space, but inside the Earth, according to one of them Study published in Nature By a team of scientists from mainly American institutions.
The remains of a massive primordial impact deep inside the Earth
At a depth of 2,900 kilometers, two large “bubbles” have aroused the interest of scientists since their discovery in the 1980s. They are located at the bottom of the Earth’s mantle, which is the layer between the Earth’s core and its crust. Each is the size of a continent and lies beneath Africa and the Pacific Ocean.
They are hotter and denser than their surrounding environment, and computer simulations suggest that these clumps are “buried traces” of Theia, which penetrated the Earth at the time of impact.
This collision “was the most violent event that the Earth has ever encountered” in its history, and what is “very, very strange” is that there are no visible traces of it.” says Qian Yuan, a geodynamics researcher at the California Institute of Technology (CalTech) and lead author of the study.
What made you wonder: “Where are the remains of the body that collided with the Earth? My answer: inside the Earth.”
Theia then collided with the Earth at a speed of more than 36,000 kilometers per hour, which is fast enough to penetrate part of it. “Deep in the nether depths of the earth.”
These pieces of essentially molten rock, several tens of kilometers across, cooled and, after solidifying, descended to the edge of the Earth’s mantle, near the core. It accreted into two different masses, each larger than the Moon, according to Yuan, who also insists that these conclusions are still the result of necessarily incomplete models and simulations.
Volcanic activity and continent formation
Theia remnants may be responsible for important processes occurring on Earth and could be an explanation for the anomalies observed at the boundary between the mantle and the core.
Bubbles are known to direct magma upward from the mantle to the surface of the Earth’s crust. It is a phenomenon linked to volcanic eruptions and also to the development of continents.
For the yuan, Theia impact ‘played role in Earth’s evolution over 4.5 billion years’. And this is what he said, It makes Earth “unique and different from other rocky planets.”
“Earth is still the only confirmed habitable planet and we don’t know why. This collision may have established the initial state of Earth’s evolution. Studying its consequences could help us discover why Earth is different from other rocky planets.”
Thus, a better understanding of the giant impact hypothesis could provide information about the evolution of Earth and other rocky planets, in our solar system and beyond.
“If our model is correct, the bubbles should contain isotopes – trace elements – similar to rocks in the lunar mantle, which could be tested on future missions to the Moon,” Yuan concludes.
With AFP and Reuters