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The Creation of Earth's Moon

At around four and a half billion years ago, Earth received a collision from an object known as Theia. The recent discovery may be able to solve the question of how the moon was formed and why it is so similar to Earth.


One of the biggest mysteries in terms of the creation of the moon and why it is possibly a mystery is that our moon is tremendously large for a moon. Most moons out there in the solar system are very small compared to Earth’s moon. Moreover, there is something else that is very unusual about our Moon. It is the fact that the composition of Earth’s moon is exceptionally similar to Earth.


The moon rocks are very similar to Earth and we could not explain how the moon was created due to this. The modern interpretation of the creation story is that once upon a time, approximately four and a half billion years ago, Earth received a collision from an object known as Theia. This object collided with Earth in such a way that it generated a huge explosion and a tremendous amount of debris that was released into the lower and higher obit of our planet. Following the collision, it eventually resulted in the creation of the new Earth and the moon. This is a very simplified version of the actual event because no matter how we look at this, some things do not seem to add up.

The creation of Earth's moon: Text
The creation of Earth's moon: Video

If this was a direct collision, the created moon would not have an orbit that it has today. It would most likely have a much lower orbit and would release all the material that would just fly away. Thus, a direct collision does not seem to explain what exactly happened.


Scientists, therefore, concluded that the collision was more likely a kind of a swipe, a sideswipe. Theia most likely passed by the side of the planet Earth and hence a lot of the material was released into the orbit. As time passed, the material eventually solidified and turned into the moon. The problem about this is that if this was a sideswipe, all of the material would have a different composition. It would not really be similar to Earth unless both planets that collided were identical; this is very unlikely. If the planets were somewhat different in composition, the moon would also be different in composition. Nonetheless, the rocks from the Apollo missions provide evidence that the moon is indeed very similar to Earth’s composition.

The creation of Earth's moon: Text
The creation of Earth's moon: Video

The collision with Theia was probably very different. According to the “Terrestrial magma ocean origin of the Moon” paper by Natsuki Hosone (Click here to access this paper: https://www.nature.com/articles/s41561-019-0354-2), the moon was created when Earth was still forming. In other words, the idea is that the Earth back then was not solid. Instead, the Earth was originally filled with magma oceans on the surface. If Theia collided with this molten lava bowl, a lot more of Earth’s material would be released into space, as opposed to the material from Theia. If Earth was originally full of molten oceans and all of the oceans were displaced and released into the outer space from the collision with Theia, this could potentially create the moon we see today. Put differently, the original collision had to be with an object that was relatively liquidy; this could be the explanation for how our moon was created.

The creation of Earth's moon: Text
The creation of Earth's moon: Video

The moon’s surface is very similar to Earth’s surface but there is one major component that is different. The moon’s surface is enriched in Ferrum Oxide, also known as Iron Oxide. This was not easy to explain until this new discovery. It shows that there is another thing that is very rich in Iron Oxide on Earth. Magma. The materials that is coming from inside our planet is usually enriched in Iron Oxide. Hence, if these materials are released into space and forms into an object, this would be a very similar composition to Earth’s moon. This would make more sense.  If Earth was indeed a molten ocean in the beginning and then received a direct collision from another object that released a lot of that magma into outer space, this would create an object like the moon.


This is the best theory that we have so far. No other theory explains everything including the Iron Oxide so well and no other theory explains all of these details that we could not explain well before. The Japanese team from Japan’s Agency for Marine Earth Sciences and Technology have found a pretty good solution and a pretty good explanation to what happened four and a half billion years ago. This also answers the question of whether there was liquid water on Earth before the collision, the answer to which would probably be no. If it was all molten and hot, there would not be any surface to have water.

The creation of Earth's moon: Text
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