How did the moon come to be?

Question: How did the moon come to be?
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- Royal Society of Chemistry: Find out more about:
  
  moon
Asked by Kim Jommy Un to Alex, Anaïs, Peter, Sarwat, Shreesha on 9 Mar 2015.
- Anaïs Pujol answered on 9 Mar 2015:
  
  The moon is the earth’s satelite. Due to that it has a lot of influence on our planet. There are several theory about its formnation:
  
  However physicists think a collision between earth and something as big as Mars. This collision would have ejected matter which have aggregated to create the moon. This theory appears in 1975 and it is currently the one the most accepted.
- Peter Maskell answered on 9 Mar 2015:
  
  I agree with anais’s answer.
- Sarwat Iqbal answered on 10 Mar 2015:
  
  The Apollo missions brought back a third of a tonne of rock from the Moon. It analysis showed that it was similar, but not the same as from Earth. If the Moon had been created elsewhere and was captured by the Earth’s gravity we would expect its composition to be very different from the Earth’s. If the Moon was created at the same time, or broke off the Earth, then we would expect the type and proportion of minerals on the Moon to be the same. But they are slightly different.
  This suggests that it was formed during an impact between the Earth and another small planet, about the size of Mars. The debris collected in an orbit around Earth and we call it moon.

Question: How did the moon come to be?