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Traces of an 'ancient alien world' have been discovered beneath Earth's mantle: the astonishing discovery

Traces of an 'ancient alien world' have been discovered beneath Earth's mantle: the astonishing discovery

In the early days of the solar system, a Mars-sized body called Theia collided with Earth, creating the Moon — new computer simulations suggest the remains of an alien planet are right beneath our feet.

According to new research and studies conducted by researchers from China, the United States and the United Kingdom, some of Theia's pieces ended up inside our Earth, and more specifically deep in the mantle, as a result of the great collision that occurred billions of years ago. If so, it would solve a mystery that has worried scientists for more than a decade: the presence of two large parts of the Earth's mantle at a depth of about 2,900 kilometers, and they do not appear to be moving as quickly as the other parts.

LLVPs – Large Low Velocity Zones

Earth is a strange world
Artistic representation of the engagement Thea – Terra. Photo credit: Hong Bing Ding, Hangzhou Sphere Studio, China

The study suggests that these dense fragments must be pieces of Theia's mantle that were preserved deep within our Earth after the impact. We know about them because the seismic waves that travel through the Earth during earthquakes move differently through different materials. Specifically through seismic data, scientists were able to obtain detailed maps of LLVPs (Great low cutting speed Counties): Large dense areas at the fundamental boundaries of the mantle, one under Africa, the other under the Pacific Ocean.


A series of computer simulations of Theia's impact were then performed and the effects it would have on Earth were subsequently observed. The first simulation suggests stratification of the Earth's mantle: Earth's material and Theia in the upper mantle would be mixed in an ocean of liquid magma, while the lower mantle would remain more solid and predominantly silicate. This stratification, based on seismic data, may still exist today. The second simulation proposes LLVPs. The team found that pieces of Thean material, only tens of kilometers in diameter, could have sunk to the core-mantle boundary and, there, accumulated, giving rise to LLVPs. Other studies say that about 2-3% of Earth's mass may have come from Theia – the LLVP material must be 2-3.5% denser than Earth's mantle, and richer in iron. This gives us a new set of tools to understand the history and formation of our planet and solar system, and to study the habitability of other planets. We have yet to find any exactly Earth-like exoplanets in the Milky Way, and Theia's massive influence may be one reason Earth is the way it is. Here is an in-depth look at the birth of the moon.

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