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A new study suggests that the moon formed after a giant protoplanet crashed onto the Earth, which was then covered with an ocean of magma. According to the study, the resulting magma splashes formed a disc around the planet that eventually fused with the Moon.
Credit: Shutterstock
There is a problem with the moon: no one really knows how it's formed, and the most popular theory – known as the hypothesis of the giant impact – does not seem to fit to modern observations of the chemical composition of the moon.
In a new study published April 29 in the journal Nature Geoscience, a team of researchers from Japan and the United States tries to solve this lunar paradox by adding an ocean of magma.
The new study begins with the standard version of the hypothesis of the giant impact, which looks as follows: Once upon a time, about 4.5 billion years ago, when the system Solar was still filled with neonatal planets, a renegade rock the size of Mars took a bad turn near Venus and crashed head-on into the Earth in formation. The broken remains of this foreign planetoid, as well as pieces of broken material that have split off the Earth, have merged into orbit around our planet and have finally become the round moon we know and love, according to the theory. [10 Interesting Places in the Solar System We’d Like to Visit]
The computer simulations of this ancient impact suggest that, if it really was so that the moon was born, most of the materials that compose it should come from the planetoid that crashed on the Earth. But recent studies on lunar rocks tell a different story. More and more researchers are discovering that the chemical composition of the Earth and the Moon is almost identical. How, then, can one make the moon mainly from the Earth and most of the time not from the Earth? Something must give.
The authors of the new study attempt to solve this paradox by setting the time of the big impact about 50 million years after the formation of the sun (towards the end of the window generally estimated) when the young Earth may have covered by a sea of magma up to 1,500 kilometers deep. In a series of computer simulations, the researchers planted a rocky protoplanet in this magma-impregnated earth, then observed the melted sea splashing space into an "arm" of giant magma.
This snapshot of the team's simulation shows a giant impactor (blue) striking a proto-Earth covered with magma (red) about 4.5 billion years ago. When large amounts of lava splashed into space, they formed a disk around the Earth that eventually fused with the Moon.
Credit: Hosono et al / Nature Geoscience
The impacted magma reached significantly higher temperatures than the rocky material of the planetoid, which resulted in an increase in the volume of magma splash during their momentum in space. At first, the researchers wrote that magma splashing followed broken fragments of the proto-planet around the Earth's orbit, but quickly passed them. While most of the protoplanet impactor finally fell back into the warm ocean of the Earth, the vast cloud of molten matter remained in orbit and finally turned into a moon. These simulations gave a moon with a much higher percentage of Earth-derived materials than previous studies.
"In our model, about 80% of the moon is made up of proto-terrestrial materials," said co-author of the study, Shun-ichiro Karato, a geophysicist at Yale University, in a communicated. "In most previous models, about 80% of the moon is made up of the impactor – it's a big difference."
According to the authors of the study, the magma-ocean hypothesis shows that the Earth's moon-like chemical composition might be consistent with the theory of giant impact. This is not yet a complete answer to the formation of the moon, but it unites a little more clearly the predominant theory with real observations.
Originally published on Science live.
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