There are a number of theories about where the Moon came from. Our best guess is that it formed when the Earth was hit by a large object called Theia. The impact projected huge amounts of orbiting debris, which eventually united to form the moon.
There is a problem with this theory. Mathematical models show that most of the materials making up the moon should come from Theia. But samples of Apollo missions show that most of the material on the moon comes from the Earth.
A paper released earlier this week in Nature Geoscience has a possible explanation. The research, led by Natsuki Hosono of the Japan Agency for Marine-terrestrial Science and Technology, suggests that the Earth at the time of impact was covered with hot magma rather than an external crust tough.
On a planetary surface, magma could be dislodged much more easily than a solid crust. It is therefore plausible that when Theia hit Earth, molten material from the Earth flew into space and then solidified in the Moon.
This theory is very much based on the timing of the formation of the moon. For the theory to be true, the Earth should have been in a zone of magmatic heat and coherence.
In addition, as Jay Melosh of Purdue University comments in an article, this new simulation still does not tick all the boxes needed to align our lunar observations with our theories. But it is an important step to bring us closer to a solution.
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