If the Moon arose from the collision between Earth and Theia, who provided more material?

A group of researchers from the Max Planck Institute for Solar System Research and the University of Göttingen, Germany, has obtained new clues about the origin of the Moon and its possible constitution. The Moon is not made of cheese, but almost entirely of the Earth’s mantle, and a tiny fraction of the natural satellite should belong to Theia, the Mars-sized body that collided with proto-Earth in the early years of its formation. .

The origin of the Moon

Earth’s Moon is special compared to the other 200 moons in the solar system. It did not emerge next to the planet nor was it a rock that was trapped by its gravitational influence. She is probably a child of the violent neighborhood that was the solar system in its early stage. The most accepted theory about the formation of the Moon is that it was created from the collision of a Mars-sized planet with proto-Earth approximately 4.5 billion years ago.

This body, known as Theia, disintegrated and regrouped with proto-Earth. Its remains became part of the interior of the planet we inhabit. After the collision, a huge amount of combined debris was also released, which cooled and formed the satellite. If this is so, a particularly provocative question arises: what is the proportion of material from Theia and proto-Earth on the Moon?

To find an accurate answer, German researchers analyzed 14 lunar samples available on Earth to record the oxygen isotopes in them. They then compared them to 191 measurements of minerals on the planet’s surface. The scientists used the method of laser fluorination, where oxygen trapped in rocks is released by a shot of light.

A cannonball straight to Earth

According to research published in the journal Proceedings of the National Academy of Science (PNAS), the Moon is mostly composed of remains of the Earth itself. The answer is simple, but it has important implications for the story of Theia’s collision. For example, this body must have been impacted when it was a piece of planet detached from its mantle. “It was like a metallic cannonball,” compare the authors of the study.

“If this were the case, Theia would be part of the Earth’s core today, and the Moon would have formed from material ejected from the Earth’s mantle. This would explain the similarity in the composition of the Earth and the Moon,” he said Professor Andreas Pack, managing director of the Center for Geosciences at the University of Göttingen and co-author of the study.

The theory of the great impact between proto-Earth and Theia has a multitude of evidence to support it. There are remnants of the Moon that have the same oxygen signatures as rocks on Earth. Even supercomputer models have confirmed that, as long as Theia was a size similar to Mars, the dynamics of the particles resulting from the impact tend to form a moon with the same proportions as the one we know.