Formation of our Moon

After planet formation, there was a period called the heavy bombardment where planets and planetesimals continued to collide with each other leaving many impact craters. Most scientists say this period was the causation of the formation of our uncanny large moon. Furthermore, they say the moon resulted from a giant impact, where a very large leftover planet-sized planetesimal collides into planet (in this case the Earth). (1) This collision would have blown out rocky debris into orbit which in turn would have formed our Moon.

There are two main pieces of support for this theory. First, the Moon’s composition is very similar to the Earth’s outer layers, as you may predict would happen if the material was blown away in a collision. (1) They have very similar densities, the only difference being that Earth’s is a bit higher because of its iron core (the Moon does not have iron had already sunk into the core by the time the collision occurred). (1) There also happens to be the same isotope composition on the Earth as on the Moon. Rock and meteorites from other parts of the solar system do not have this same isotope composition, indicating the Moon formed from material close to the Earth.

(2) Secondly, the Moon has much fewer easily vaporized ingredients than the Earth. This would make sense since the heat produced during the impact would have vaporized the ingredients. And now you may ask the question: what is the reason for the Moon’s abundance of craters as opposed to the Earth’s lack of craters? (2) Simply put, the impact craters are not as the visible on the Earth due mostly to erosion and partly plate tectonics, neither of which exist on the Moon.

It should be noted that the giant impact theory is the leading hypothesis for the formation of Moon, meaning it may be subject to change in the future. However, the hypothesis is able to explain very well just why the Earth’s Moon is a unique case in our solar system. (1) And considering the hypothesis has stood fairly firm for 25 years, it will take very careful research to be refuted.

References:

1.) Hartmann, William and Herres, Gregg. “The Origin of the Moon.” 2004. Psi.edu. 2 Apr. 2009.

2.) Bennett, Jeffery. The Cosmic Perspective: The Solar System. 5th ed. Benjamin Cummings.