A new study suggests that the moon was formed after a giant protoplanet crashed into Earth, which was later covered in a magma ocean. The resultant spikes of magma formed a disk around the planet that finally was united to the moon, according to the study.
There is a problem with the moon: no one really knows how it was formed, and the most popular theory, known as the giant impact hypothesis, does not seem to coincide with the modern observations of the chemical composition of the moon.
In a new study published on April 29 in the journal Nature Geoscience, a team of researchers from Japan and the United States try to solve this lunar paradox by adding an ocean of magma to the mix.
The new study begins with the standard version of the giant impact hypothesis, which happens as something like this: It was once, about 4,500 million years ago, when the solar system was still full of baby planets, one Reluctant rock is approximately the size of Mars took a wrong turn near Venus and broke off from the ground still forming. The theory continues with the remains destroyed by this alien planetoid, along with some pieces of broken matter that were separated from the Earth, that were united in orbit around our planet and, finally, they became the round and marked moon that we know and love. [10 Interesting Places in the Solar System We’d Like to Visit]
The computer simulations of this ancient impact suggest that, if it were really the shape of the moon, most of the material that constitutes the moon should have come from the planetoid that crashed into the Earth. But recent studies on lunar rocks relate a different story. Increasingly, researchers find that the chemical composition of the Earth and the moon are almost identical. How, then, can the moon make the majority of the Earth and, mainly, the Earth at the same time? Something must be given.
The authors of the new study are trying to solve this paradox by establishing the time of great impact about 50 million years after the formation of the sun (towards the previous end of the typically estimated window) when the young Earth would have been covered by a sea of magma of up to 1,500 kilometers deep. In a series of computer simulations, the researchers launched a rocky protoplanet in this magma-covered Earth, and then saw the sea out of space in a giant "arm" of magma.
The affected magma reached temperatures significantly higher than the rocky material of the planetoid, which caused the magma jump to expand in volume as it emerged in space. Initially, the researchers wrote, the splash of magma followed the broken pieces of the proto-planet around the Earth's orbit, but quickly overcame them. While most of the protoplaneta impactor finally fell back to the warm ocean of Earth, the vast cloud of fused material remained in orbit and eventually gathered on a moon. These simulations resulted in a moon with a much larger percentage of material derived from the Earth than the previous studies.
"In our model, about 80% of the moon is made of proto-terrestrial materials," Shun-ichiro Karato, a geo-physicist at the University of Yale, said in a statement. "In most of the previous models, about 80% of the moon is made of impact. This is a big difference."
According to the authors of the study, the magma-oceanic hypothesis shows that the chemical composition similar to Earth of the moon could be compatible with the theory of giant impact. It is still not a complete answer to how the moon formed, but it unites the predominant theory with real observations somewhat more clearly.
Originally Posted in Live sciences.