Explanation for the similarity between the composition of the earth and the moon

The protoplanet with which the early Earth collided to form the moon, according to the most widely accepted theory, probably had an Earth-like composition, according to simulations published Wednesday in Nature.

The research describes how the similarities between the Earth’s mantle and the Moon may have arisen. If the moon was indeed formed by a collision between the proto-Earth and a planet-like object the size of present-day Mars, then it would make sense that most of the moon’s material consists of material from the impacting object. Strangely enough, the samples from the moon are suspiciously similar to the composition of the Earth’s crust. Other bodies in our solar system have a very different composition.

The rotated simulations of planet-forming regions show that different planets formed during the same simulation have different compositions. Strikingly, large objects impact significantly more often on planets with a similar composition, so that the similar composition between the moon and Earth may be a natural result of that late, large impact.

A collision between two planetary bodies of similar composition, leading to the formation of the moon – Credit: Hagai Perets