The moon is believed to have been born from the impact of another celestial body with the Earth that occurred 46 billion years ago.Although this giant collision hypothesis can explain various characteristics of the present Earth and the Moon, it has been reported to be inconsistent with the isotope ratio measurement results of various elements contained in the rocks brought back from the Moon by the Apollo program.Computer simulations of the giant collision hypothesis predicted that the lunar material would be the celestial body on the side of the collision, but the observations of the lunar rocks were in good agreement with those of the Earth.

　As an element to solve this contradiction, this research group focused on magma ocean.It was predicted that the simulation results of the giant collision would change by adding the effect of the magma sea, which is said to have covered the surface of the primitive Earth.

　The research group improved the model based on the conventional standard giant collision hypothesis, and conducted the world's first computer simulation of a giant collision under the assumption that there is a magma ocean on the primitive Earth.As a result, it was found that the magma ocean greatly contributes to the formation of the moon.Examination at various collision angles and velocities also showed that the presence of magma oceans increases the proportion of matter derived from the Primitive Earth among the materials of the Moon.In other words, it was suggested that the contradiction of "the problem of isotope ratio between the earth and the moon" pointed out in the conventional simulation can be solved by the existence of magma ocean.

　The results of this research will bring about different results from the early Earth that has been considered so far, and will be a great clue to know how the present Earth was formed.

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