http://ukrnovosti.com.ua/images/news/luna.jpg
The results of isotopic analysis of rocks of the Earth and moon, by the American chemists, confirmed a theory of the origin of the moon – the collision hypothesis, were previously questioned. A study published in the journal Nature.
Since the mid 1970-ies became widespread idea that the Moon was formed after collision of proto-Earth with an object comparable in size with Mars. This theory is well explained, some features of our satellite, for example, its significant (compared with Earth) size.
However, in 2001 a group of scientists said that the chemical compositions of rocks of the Earth and moon are virtually identical. Scientists have compared the composition of terrestrial rocks and samples obtained during the lunar missions. The results of the analysis contradict the numerous models, showing that 60-80% of the material that formed the moon was not the Earth, and faced with her heavenly body. However, the bodies formed in different parts of the Solar system, differ significantly from each other in isotopic composition. This option is similar to the fingerprints – it helps scientists to trace the evolution of the heavenly bodies, and to note instances of collision with other bodies. Thus, the hypothesis of a collision was questioned.
Later it turned out that small differences in the content of isotopes in the Earth and the moon were unavailable for study due to a lack of perfect detection of isotopes. In 2015, geochemists kun Wang Washington University in St. Louis, and Stein Jacobsen, Harvard University Professor, developed the technology with precision ten times greater than existed at the time. Scientists have found differences between the rocks on the Earth and the moon, which is a proof of modifications of the model of "giant impact". According to this hypothesis, the impact was so strong that the rocks of the Earth and cosmic bodies with which the collision occurred, passed into the gaseous state and mixed. This resulted in the gas cloud from which later formed the Moon. The mixing of matter of cosmic bodies explains the similarity in the chemical composition of the Earth and the moon, noted the study authors.
source: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature19341.html