Experts from the University of Bern in Switzerland, believe that the Earth was originally orbited by two moons.

(The researchers are attempting to explain why the far side of the Moon has a thick, mountainous crust while the near side is flat.

The mountainous far side of the moon:-

The smoother near side of the moon:-

The theory is that the smaller moon was absorbed into the larger when they smashed together in slow motion, around 4.4 billion years ago.