The Origin of the Moon explained


Many of us ask ourselves how the moon came to exist and haven’t found an answer or existing explanations satisfactory. This is the reason why scientists made a new analysis that strengthened the Giant Impact Hypothesis, which suggests that it was formed as a result of a collision between young planet Earth and a protoplanet.

With the Earth Being approximately 4.5 billion years old, scientists think the moon was formed a short while afterwards. The most popular explanation for the origin of the moon is the Giant Impact Hypothesis that was proposed in 1970. This theory suggests that the moon was formed a result of collision between two embryonic worlds, or protoplanets. One of them was infant Earth and the other a Mars-sized object known as Theia. The moon was formed from a coalescing of the debris.

The theory then says that at least 60 percent of the moon should be made of material from Theia. Because most of the objects in the solar system have unique chemical makeups, the moon and Theia should also contain such chemicals. However, rock samples from the moon indicate that it’s more similar to earth in terms of isotopes than the models say.

The study leader of a study recently conducted to ascertain this, Alessandra Mastrobuono-Battisti, also an astrophysicist at the Israel Institute of Technology, Haifa, says that the chemical composition of the Earth and moon are similar, and differ by very few parts in a million.

Violent Birth

Mastrobuono-Battisti and her team simulated collisions in a solar system comprising of 85-90 protoplanets- each with the mass equal to that of planet earth, and 1000-2000 smaller bodies known as planetesimals– each with a mass 0.25 Earth.

The researchers simulated the collisions taking place in a disk pattern extending from 0.5-4.5 (AU) Astronomical Units (1AU=distance from earth to moon, approximately 93-150 million kilometers).

The study found that 100-300 million years after the models began, each of them produced three to four rocky planets, the largest one having a mass equal to that of Earth. Each protoplanet was made of material different from the other, and 20-40 percent of the time, the planet that collided had material very similar to the protoplanet it collided with.

The similarity is a result of the orbit each colliding body occupied. The amount of heat received also determined the composition of a body; if far from the sun, it would be colder and thus have high chances of retaining a relatively heavy Oxygen isotope. According to the scientists, as each planet assembled, the last planet to collide with it shared a similar orbit. This means that planets with similar compositions may share the same birthplaces.

The findings support the idea that the similar composition between the moon and earth could be as a result of a giant collision. The theory also explains why the composition of the two differs from that of other bodies in the solar system. This research was documented in the April 9 issue of Journal nature.

There are also other theories that explain the origin of the moon, but these are less popular.

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About the author

Diana Florence is an Apollo Bay, Australia part time freelance writer that has covered several topics including technology, health, science, finance and sports. She is also part time writer for some local editions including Colac Herald and Geelong Advertiser. Diana graduated from the University of Exeter with a bachelor of arts in International Relations.