The Moon was not always linked to the Earth, there was a time in the history of our planet when it did not have a natural satellite. But then, something strange happened and a body a quarter of the diameter of the Earth formed and began to dance eternally around it. Although scientists are still not quite sure how the Moon formed, here are some of the most accepted theories.
The giant impact hypothesis
The Moon formed one hundred million years after the creation of the Solar System, so researchers have been wondering how it could have emerged in the middle of an already configured system. That is, the Moon did not come from the planetary formation events that occurred at the birth of the Solar System, so where could it have emerged from?
There is one that is so far the most accepted among the community of astronomers. This suggests that the Moon was formed when an object crashed into a still very young Earth.
Our planet, like all others in the Solar System, was formed from a leftover cloud of dust and gas, something astronomers call a protoplanetary disk, that rotated around the Sun. In this period in the history of our cosmic home, The state of the system was very violent, so several bodies were created that were never completely consolidated.
It is precisely thought that one of these protoplanets could have crashed into the Earth when it was still very young. Astronomers have named this body Theia, it is believed that it was at least the size of Mars and that it collided obliquely with a young Earth. As a result, two large pieces of Theia broke off and were expelled, forming two moons that would later merge into our current Moon.
This theory would explain why the Moon is the largest natural satellite in the entire Solar System in relation to its host planet. In addition, it would also explain why the Moon is made up of lighter elements which makes it lighter than the Earth.
Until now this is the theory about how the Moon formed, most accepted by the scientific community, although it also has its detractors. The contradictions arise from the fact that the Moon and the Earth are almost twins in terms of their compositional elements. In that sense, some astronomers suggest that if it had happened as the hypothesis says, at least 60% of the lunar composition should come from the composition of Theia, but this is not the case.
Conformation hypothesis
Although the Theia hypothesis is so far the most accepted, there are other hypotheses that could explain how the Moon formed. One of them is the conformation theory, which basically says that both the Earth and the Moon were formed at the same time when the Solar System was a very violent and primitive place.
According to this theory, gravity would have caused protoplanetary particles to come together at the same time to form the Earth and, at the same time, its natural satellite. From this perspective, it would explain the very similar composition between the Earth and its Moon, as well as the location of the natural satellite.
Although it is a hypothesis that could explain the similar compositions between the planet and its satellite, it faces a major failure; Although the Moon and the Earth are almost twins in composition, the former is much less dense than our planet, which would probably not be the case if both had begun their formation at the same moment in cosmological history.
The capture
There is a last hypothesis that explains that the Earth could have captured an object that passed near it with its gravity. It is known that other moons in the Solar System arose in this way, for example the Martian moons Phobos and Deimos arose in this way.
This hypothesis would explain why the Moon is much less dense than the Earth, but it has a great unknown that it does not resolve; the shape of the satellite. Normally when a moon arises as part of the capture by gravity, its shapes are completely irregular and do not have a spherical shape as is the case with our Moon. Furthermore, their paths do not tend to align with the planet’s ecliptic, which does happen with the Moon and Earth.
Currently the hypothesis that leaves the fewest questions unanswered is that of the giant impact. Therefore, it is very likely that the Earth’s natural satellite arose from the collision of Theia with the planet, although there is still more research needed to verify the hypothesis and finally understand how the Moon was formed.