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Moon 'Formed When Earth Struck Mini-Planet'
The Moon may have been created by a collision between Earth and a giant planetary rock, according to new research.
The celestial body called Theia smashed into Earth 4.5 billion years ago and scientists suggest the resulting debris then formed the moon - a theory known as the Giant Impact Hypothesis.
Newly analysed samples from the Moon's surface on Apollo 11, 12 and 16 missions found it could be equally formed from Earth and Theia fragments.
It was previously thought that the Moon was formed mostly by Theia, with only 10-30% coming from Earth.
Scientists examined various oxygen atoms and found Moon rocks have a different makeup than Earth rocks, suggesting the surface of the Moon contains material from the body which collided with Earth.
The findings state: "They were able to detect a slightly but distinctly higher composition of the oxygen isotope in the lunar samples.
"This very small difference supports the Giant Impact Hypothesis of Moon formation."
The author of the report, Daniel Herwartz from Georg-August-Universitat Gottingen, said: "The differences are small and difficult to detect, but they are there.
"We can now be reasonably sure that the Giant collision took place."
The study has been published in the journal Science and researchers will conduct further tests to confirm the findings.
The findings will be presented in California at the Goldschmidt geochemistry conference on June 11.