The hypothesis that a large object hit the Earth 4.5 billion years ago, generating piles of debris in space that eventually formed the Moon, is one of the best known.
New evidence, however, points out that pieces of a large Mars-sized fragment called ‘Theia’ also ended up lodged inside the Earth.
What does that mean
- If confirmed, the find could solve a great mystery that has intrigued experts for more than a decade: the origin of giant, dense bubbles buried about 2,900 kilometers deep in the Earth’s mantle.
- These bubbles that surround the core of our planet are known by the acronym LLVPs (large low-shear-velocity provinces).
- Using seismic data, scientists were able to map bubbles on the boundary between the Earth’s core and mantle — one of them is under Africa and the other under the Pacific Ocean.
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The giant impact that formed the Moon appears to be the origin of the early mantle and marks the starting point for Earth’s geological evolution over 4.5 billion years
Hongping Deng, researcher at the Chinese Academy of Sciences.
Until now, experts believed that LLVPs were generated by internal Earth processes, such as remnants of ancient plate tectonics or a magma ocean at the base of the mantle. But the team behind the new discovery thought something else might have contributed to the formation of LLVPs: fragments of Theia.
Although simulations indicate that most of what was left ended up incorporated into the Moon, and only traces remained on Earth, researchers are working with the possibility that a large amount was trapped inside the Earth, where it remains to this day.
The discoveries
Through a series of computer simulations — of the impact and observing the effects it had on Earth — researchers found signs that the giant impact may have left traces in the composition of our planet.
- The first is the stratification of the Earth’s mantle.
- In the simulations, material from Earth and Theia mixed in the upper mantle in an ocean of liquid magma, while the lower mantle remained more solid.
- The team also discovered that pieces of material from Theia, tens of kilometers in diameter, could have sunk to the Earth’s core/mantle boundary.
- There, they accumulated, turning into dense, iron-rich giant bubbles (the LLVPs).
“We hope that future missions can obtain rocks from the lunar mantle to compare them with mantle bubbles to see if they share the same chemical signatures,” Qian Yuan, geophysicist and lead author of the study, told ScienceAlert.
If this is the case, the discoveries could help to understand the history and formation of our planet: “The ancient collision that forms the Moon may have had a lasting effect on the entire evolution of the Earth (…) it may be a fundamental factor in the why Earth is geologically different from other rocky planets”, concludes Yuan.
The research was published this Wednesday (1st) in Nature.
