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Researchers at the University of California, Los Angeles, show that the moon was created by a head-on collision between earth and a new planet called Theia. While the current study suggests a direct collision, earlier it was believed that the violent event that happened about 100 million years after the earth was formed happened at an angle of 45 degrees or more.

Scientists based their research on the analysis of seven rocks from the moon during the Apollo 12, 15 and 17 missions, along with six volcanic rocks from the earth. An analysis of the oxygen atoms of the rocks showed that the team could compare the isotopes of these atoms in the earth and the moon.

"We don't see any difference between the earth's and the moon's oxygen isotopes; they're indistinguishable," Edward Young, lead author of the study, said in a press release.

The similarities between the oxygen in rocks on earth and the moon seem to indicate a head-on collision. If there had been a "side blow at an angle of 45 degrees or more" it would have led to the moon being comprised majorly of the forming planet Theia. Hence, various oxygen isotopes would be observed on the earth and the moon.

"Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them," Young said. "This explains why we don't see a different signature of Theia in the moon versus the Earth."

If the crash had not occurred, Theia would have grown into a planet, said Young.

The findings were published in the Jan. 29,2016 issue of Science.