Scientists on Wednesday proposed a new theory that could solve two mysteries at once: one about the origin of the Moon and the other about the bowels of the Earth.
Two mysteries that will be solved soon? Scientists put forward a new theory on Wednesday, November 1, that answers two questions: How did the moon appear? Why are two large “points” hidden in the center of the Earth?
As for the first mystery, the origin of the Moon, the most plausible theory is that it appeared after a forming planet collided with the future Earth 4.5 billion years ago. A collision with Theia, a Mars-sized protoplanet, would have propelled enough material into space to form the Moon.
The remains of Thea remained to be found. By looking not in the air, but under the ground, according to the study published by a team of scientists from American institutions in the journal Nature.
Located 2,900 kilometers below the surface, they have intrigued scientists since they were discovered using seismic waves in the 1980s. Located at the bottom of the Earth’s mantle – the layer that separates the Earth’s core from its crust – these continental-sized blocks lie. Under Africa and the Pacific.
They are warmer and denser than their surrounding environment. Computer simulations conducted by the researchers indicate that these masses are “buried traces” of the planet Theia, which entered Earth at the time of the collision.
Qian Yuan, a geodynamics researcher at the California Institute of Technology (CalTech) and first author of the study, told AFP that this collision was “the most violent event the Earth has ever experienced” in its history.
Which makes it “very, very strange” that no visible trace remains, he said. What made him think: “Where is the impactor? My answer: Under the ground.”
Between space and geology
The research led experts from two very distinct disciplines, space and geology, to collaborate.
During its formation, Theia collided with the Earth at more than 36,000 kilometers per hour, fast enough for part of the impact body to penetrate “a great depth into the Earth’s lower mantle.”
These pieces of essentially molten rock, several tens of kilometers across, cool and solidify, descending to the boundaries of the mantle and the Earth’s core. This was helped by the presence of a greater percentage of iron oxide than found in the terrestrial environment, which made it heavier.
It has accumulated into two distinct masses, each larger than the Moon, according to Qian Yuan, who also insists that these conclusions remain the product of necessarily incomplete models and simulations.
An expert in Earth sciences and planetary exploration at the University of Stirling in Scotland told AFP that the theory put forward by Qian Yuan “is consistent with many existing pieces of evidence.” “This is an important result,” said Christian Schroeder, who was not involved in the study.
Even if this theory does not solve, in his opinion, the question of the origin of the Moon, it provides “a reliable explanation for the anomalies observed at the boundary between the mantle and the core.”
As for Theia’s remains, they may be “responsible for important ongoing processes on Earth.”
It is known that the blocks carry columns of mantle, and magma rises, to the surface of the Earth’s crust. It is a phenomenon linked to volcanic eruptions and also to the development of supercontinents.
For Qianyuan, Theia’s impact “played a role in the Earth’s evolution over 4.5 billion years.” This is what makes it, according to him, “unique (…) different from other rocky planets.”
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