A protoplanet collided with Earth about 4.5 billion years ago, an impact from which the Moon was born. A team of scientists has presented a new theory that the remnants of that protoplanet are still in the depths of the Earth, according to a material published by the journal Science and taken over by Live Science.
If the remains of this protoplanet, called Theia, were preserved after the impact, it could be the explanation for the two conglomerates of hot, continental-sized rocks currently in the Earth’s mantle – one under Africa and the other under the Pacific. If they were on the Earth’s surface, these formations would be 100 times higher than Mount Everest, according to Live Science.
The impact with Theia led to the formation of the Moon and turned the Earth’s surface into an ocean of magma, and some scientists believe that these rock conglomerates formed as this ocean of magma cooled and crystallized, according to material published by Science. Other researchers believe that these conglomerates would have been unaffected by the collision with Theia, remaining for billions of years near the center of the Earth.
One week ago, at the Lunar and Planetary Science Conference, a doctoral student named Qian Yuan of Arizona State University (ASU) Tempe presented an alternative hypothesis.
He proposed that, after the impact that led to the formation of the Moon, dense materials from the mantle of the protoplanet Theia sank to great depths below the earth’s surface, accumulating in the form of these rock conglomerates positioned under Africa and the Pacific. According to the theoretical model presented by the Yuan, the rocks that are 1.5% to 3.5% denser than the matter in the earth’s mantle did not mix with the surrounding rocks. Instead, these rocks from Theia sank to the lower edge of the Earth’s mantle, near the Earth’s core.
“This crazy idea is at least plausible,” Yuan told Science magazine.
A 2019 study, published in the journal Geochemistry, supports this hypothesis, according to which the mantle of the protoplanet Theia was denser than that of Earth – by about 2% – 3.5% denser, Science reports.
The authors of the study drew conclusions about the size and chemical composition of the protoplanet Theia from the analysis of selenium rocks brought to Earth by Apollo missions, rocks that contain much more light hydrogen compared to heavy hydrogen than terrestrial rocks (light hydrogen and the hardest differs by the number of neutrons in the atomic nucleus).
Given that the selenium rocks contain an abundance of light hydrogen, it means that Theia was a large protoplanet, close to those of Earth at the time of the collision between the two bodies. In addition, Theia was a very arid protoplanet, because the water formed in interstellar space would contain a heavy isotope of hydrogen, called deuterium, which was not part of the protoplanet Theia, according to the conclusions of the new study. Also inside the protoplanet was a dense, iron-rich mantle, according to Science.
According to Yuan’s theory, while lighter, less dense rocks were projected into Earth’s orbit where they formed the Moon, pieces of the protoplanet’s iron-rich mantle sank into the Earth’s mantle where they remain to this day. in the form of rock conglomerates under Africa and the Pacific. “I think the idea is completely viable until someone else proves it to me,” Edward Garnero, a seismologist at ASU Tempe who did not participate in the study, told Science.
Source: Agerpres
Image by David Mark from Pixabay
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