Scientists have discovered that the moon came to exist after the Earth clashed with a primordial planet which had a very similar composition to the one of our planet. The study appeared on Thursday in the journal Nature. Researchers discovered this while they were trying to find the answer to the question why the chemical composition of Earth and lunar rocks is so similar.
The Primordial planet Theia is thought to have collided with baby Earth. The collision generated a cloud of debris which led to the formation of the moon. Theia was a shattered impactor which is believed to have had a different isotopic structure than the Earth’s.
One of the authors of the study, Hagai Perets, explained that since the impactor had a different composition from the Earth the moon too is expected to have a different composition. However, this does not apply in reality. The Earth and the moon are almost identical and this is the most challenging thing for the giant impact hypothesis.
Astronomer Alessandra Mastrobuono-Battisti together with his colleagues used an advanced computer modeling and created dozens of simulations of the formation of later-stage planets. Scientist noticed that usually within 100 million to 200 million years each simulation produced three or four rocky planets. The planets formed as a result of colliding embryos and planetesimals. Analyzing the formation of the moon the researchers have established that Earth and Theia had the same composition.
This resemblance could be accounted for if we consider that Theia and Earth formed from the same type of orbiting proto-planetary material since they are almost at the same distance from the Sun. According to the model there are 20% to 40% chances that the moon was formed as a result of the impact between such similar proto-planets. Mastrobuono-Battisti explained that it is common for the impactors to be more similar to the planet which they impact and not to other planets in the same system.
Perets remarked that the moon and the Earth are not twins from the same planet, but since they grew up in the same environment they can be called sisters. He also added that he is more positive about the giant impact hypothesis.
A challenge which scientists are faced with is the problem of what happened after the clash. Some scientists say that both the moon and The Earth accumulated a large quantity of extra matter during an ulterior period in which the celestial bodies were bombarded by a large number of meteorites. However such a process should have left a trail, but no evidence of it has been reported so far.
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