Scientists believe that about 4.5 billion years ago, something big hit the Earth and flipped it over the kettle on its rump. The result was a pile of debris thrown into space, orbiting until it formed the Moon. Nothing special remains of the large Mars-sized body called Theia. At least that’s what we thought.

Researchers from China, the US and the UK have found evidence that fragments of Theia entered the moon. Data also shows that fragments of Theia also fell into the Earth’s interior. If so, the giant impact hypothesis could solve a mystery that has baffled scientists for more than a decade: the existence of curved, dense, continent-sized chunks of material buried deep about 2,900 kilometers (1,800 miles) beneath the Earth’s mantle. around its core.

“Our findings challenge the conventional view that a massive impact homogenized the early Earth,” says Hongping Deng of the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences.

“Instead, the massive impact that formed the Moon appears to be the source of early mantle heterogeneity and marks the starting point of Earth’s geological evolution over 4.5 billion years.”

Droplets orbiting the Earth’s core are known as large low shear velocity regions, or LLVPs. We know these because seismic waves traveling through the Earth from earthquakes travel differently in different materials. Thanks to seismic data, scientists were able to obtain detailed maps of the LLVP: large, dense regions at the interface of the core and mantle, one under Africa and the other under the Pacific Ocean.

Previously, scientists had suggested that LLVPs were produced by some internal processes of the Earth, such as the remnants of ancient tectonic plates, hotspots, or a magma ocean at the base of the mantle. But the team behind this latest discovery believes something else may have contributed to the formation of LLVP: Theus. Previous numerical simulations had shown that most of Theia remained on the Moon, leaving only traces on Earth. However, this is not necessarily the case.

So, for several years, researchers have investigated the possibility that a large amount of Theia was trapped inside Earth, where it remains to this day, which has troubled scientists. They ran a series of computer simulations of the collision with Theia and observed its effects on the simulated Earth. And they found several indications that the giant impact may have left long-lasting scars on the Earth’s structure.

The first is the separation of the Earth’s mantle into layers. In the simulations, materials from Earth and Thea mixed in an ocean of liquid magma in the upper mantle, while the lower mantle remained Earth’s harder, mostly silicate material. Based on seismic data, this stratification may still exist today.

The second is LLVP. The team found that only fragments of Teynian material tens of kilometers in diameter could sink to the core-mantle boundary. They accumulate there and turn into LLVP. Researchers found that about 2-3 percent of Earth’s mass may have come from Theia. The LLVP material is expected to be 2-3.5 percent denser and more iron-rich than Earth’s mantle. This is good news because it means there is a way to test this.

“In most simulations of the impact that formed the Moon, most of the lunar material came from the impactor, so we expect future missions to pick up rocks from the lunar mantle and compare them to mantle droplets to see if they share the same chemicals,” Qian Yuan, a geophysicist at the California Institute of Technology, told ScienceAlert. He said he had the signatures.

If so, it gives us a new set of tools for understanding the history and formation of our planet and the history and formation of the solar system. And this could help us understand other worlds and the possibility of habitability in the wider galaxy. We have not found any Earth-like exoplanets in the Milky Way. A massive impact could be one of the reasons why the Earth is the way it is.

“The ancient collision that led to the formation of the Moon may have had long-lasting effects on the entire evolution of the Earth,” says Yuan. “Therefore, it may have been one of the key factors why the Earth is geologically different from other rocky planets.” Source