Bubbles on Earth could be the answer to the origin of the Moon – 11/01/2023 – Science

Two gigantic bubbles of viscous matter located almost 3,000 km deep could be proof that a protoplanet collided with the Earth 4.5 billion years ago, giving rise to the Moon. The hypothesis was presented by a group of scientists this Wednesday fair (1).

The main theory is that the satellite appeared when a body the size of Mars collided with the still-forming Earth.

According to this thesis, following the collision with the protoplanet Theia, a huge amount of light materials, such as silicates, were launched into space and orbit and, under the action of gravity, coalesced, leading to the formation of the Moon.

Theia’s densest and heaviest core, composed of iron and nickel, entered the depths of the Earth, which explains the difference in density between the planet and its natural satellite.

Despite decades of effort, scientists had still failed to find evidence of Theia.

But now research led by scientists from the United States and published in Nature suggests that the evidence is two bubbles of material different from the one present in their surroundings. Both are buried 2,900 km away and their existence, although known for four decades, no one had been able to explain until then.

Each of the bubbles, very flat and shaped like tears, is the size of a continent. They are located at the limit between the mantle and the Earth’s core. One is under Africa and the other under the Pacific Ocean.

Scientists have determined that the bubbles are much hotter and denser than the surrounding rock, but almost everything about them remains a mystery.

New research suggests that both are “buried relics” of Theia.

Qian Yuan, a geodynamics researcher at the California Institute of Technology and lead author of the work, told AFP it was “very strange” that no evidence of Theia’s impact had been found.

It was during a lesson taught by a planetary scientist about this mystery that Yuan first had a glimpse of an answer: “Where is the impact maker? My answer is: it is on Earth.”

Since then, research has required experts from usually separate fields, such as astronomy and geology, to join forces.

Yuan recalled that the collision theory says that Theia collided with the proto-Earth at more than 35,000 km/h and that the denser materials melted from the heat of the impact and sank “very deep into the lower mantle”.

Over the years, this material accumulated in two bubbles, located at diametrically opposite points.

The scientist stated that proving a theory that dates back to facts so distant in time and with possible evidence buried so deeply is difficult and, therefore, may not be 100% certain. But if so, the implications could prove gigantic.

The Theia collision, believed to be Earth’s last major creation event, significantly changed the planet’s composition in just 24 hours, Yuan said.

“My feeling is that this initial condition is why Earth is unique, why it is different from other rocky planets” in the solar system, he said.

The bubbles have been observed to send columns of magma to the surface and have also been linked to the evolution of supercontinents, which scientists link to the evolution of life.

Theia “left something on Earth and that played a role in the next 4.5 billion years of evolution,” Yuan said.

Christian Schroeder, an expert in Earth science and planetary exploration at the University of Stirling in Scotland, told AFP the theory “fits a lot of evidence.” “It’s a very significant finding,” he said, who was not involved in the study.

The expert also highlighted that the mystery of the Moon’s formation has not been solved, but this research gives more weight to the Theia impact theory and, at the same time, provides “a reliable explanation for these anomalies at the boundary between the core and the mantle.” .

The remains of Theia “may be responsible for important processes on Earth that continue to this day,” Schroeder added.