The “big impact” formed the Moon and left deep marks on the Earth. I study

The “big impact” formed the Moon and left deep marks on the Earth.  I study

In a study published in the journal Nature, researchers say that fragments of the protoplanet Theia, which collided with the Earth 4.5 billion years ago, could have survived the collision, but at a very deep depth, at the border between the Earth’s mantle and the Earth’s core. At a depth of about 2,900 kilometers below the surface

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Where does the moon come from? The most widely accepted theory is that about 4.5 billion years ago, a Mars-sized protoplanet collided with Earth, and that some of the resulting debris, launched into its orbit, came together to form the Moon. This idea, known as the “big shot,” would explain a lot about the origin of the Moon. But scientists still lack convincing evidence to prove the theory, such as a crater or piece of a protoplanet called Theia. However, in a study published in the journal Nature, researchers report that parts of Theia survived the impact, but very deep, at the boundary between the Earth’s mantle and the Earth’s core, about 2,900 kilometers below the surface. lhave The New York Times reported.

Where’s Thea?

“We examined the depths of the Earth – and found large ‘chunks’ of Theia,” said Qian Yuan, a postdoctoral researcher at the California Institute of Technology, who led the study. Yuan’s interest in the subject began during a planetary geochemistry course. He took it as a student at Arizona State University. On that occasion, the professor asked a simple question: Where is Thea now? “I was really inspired by this idea,” said Yuan, who has been trying to give an answer ever since. Part of Theia now makes up the Moon, but if Theia had been the size of Mars, about 90% of its mass would have ended up on Earth. Some of that mass would have melted away and mixed with Earth’s minerals, but perhaps some “chunks” of the protoplanet would have survived intact. almost.

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Tozo and Jason

Yuan wondered whether these “pieces” constitute the two mysterious structures located deep in the Earth, at the border between the core and the mantle. The spots – one under West Africa, the other under the Pacific Ocean – span an area the size of a continent and extend hundreds of miles up into the Earth’s mantle. They were first observed half a century ago, when researchers realized that seismic waves slowed down once they passed through these regions, but little is still known about their structure. In fact, seismic data allows us to perform a kind of ultrasound of the planet, providing blurry and ambiguous views of the structure without giving indications of other aspects such as temperature. Another major difficulty is that it is still impossible to drill very deeply to take samples. The land mass beneath West Africa is known as Tuzo, after c. Tuzo Wilson, Canadian geophysicist who pioneered the theory of plate tectonics. The other, located deep in the Pacific Ocean, is called Jason, named after W. Jason Morgan, who proposed that hotspots originated from plumes of material rising from the deep mantle. Some scientists have suggested that Tuzo and Jason may have been made up of “primordial” Earth—crystallized bits of a magma ocean that once covered the surface and never mixed with the rest of the mantle. Others have speculated that the structures could be pieces of oceanic crust submerged in the Earth’s mantle.

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During his observations, Yuan noted that the size of Tuzu and Jason was roughly similar to the size of the Moon. This is a consideration that led him and his colleagues to wonder whether pieces of Theia could exist on Earth. During the research, scientists conducted a series of computer simulations, breaking Theia and Earth into pieces and observing the movement of the latter during and after the collision. According to simulations, when Theia collided with Earth, the impact melted the Earth’s crust and outer mantle, mixing them with Theia’s fragments. The moon formed from that cloud of debris. The simulations also showed that more than 10% of Theia’s mantle may have become “embedded” in the Earth’s mantle. Because Theia’s mantle is thought to have been richer in iron than Earth’s, those denser parts likely sank to the boundaries of Earth’s core mantle. Then the convection that occurred in the mantle swept the fragments of Theia into Tuzo and Jason. “Our study cannot rule out other causes,” Yuan admitted. At the moment, this is still only a hypothesis, but the results obtained could prompt scientists to look more closely at how the “big collapse” affected the movement of tectonic plates. “It may have had long-term effects on the subsequent evolution of the Earth,” Yuan explained.

20070303 - Milan - Lunar eclipse.  A phase of the lunar eclipse this evening.  Daniele Dal Zenaro/ANSA

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