How was our Moon formed?

Through the early years since the dawn of humanity, early as well as modern astronomers have often documented the moon and wondered about the structure of the floating celestial body in the sky. Each of us has at one time wondered about the beauty of this celestial rock, having made its way into various facets of human culture. However, one of the most intriguing yet unanswered questions remains of how the moon was formed in the early solar system?

Various theories over the years have been proposed to understand this particular phenomenon. One such theory is the "Giant Impact Hypotheses", supported by majority of the scientific community.

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This theory suggests that the moon was formed when a protoplanetary body smashed into the early Earth. During the formation of the Solar System, the stellar medium was a violent environment and consisted of a number of protoplanetary bodies. These bodies would often collide with each other due to their own gravity and one of them supposedly also collided with the Earth. The latter may have had occurred not long after the Earth had formed.

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A mars-sized proto-planetary body named "Theia" collided with the Earth, resulting in the spread of vaporised planetary chunks into the vicinity of Earth. The planetary chunks consisted of gas, dust, and, molten rock which bounded under their own gravity formed a ring of dust around the planet.

Image Credit: NASA/JPL-Caltech.

These rings are known as "Lunar Synestia". In a period of hundred years, the disk coalesced under its gravity resulting in the formation of the moon that we see today. The newly made lunar surface consisted of a thick crust made up of a light-coloured mineral called "Feldspar" giving the lunar body its bright appearance. Collisions of the body with asteroids resulted in the generation of craters and impact basins which in turn resulted in (Image credit: Hagai Perets) lava which made Maria.

Formation of the Moon according to " The Great Impact Hypothesis"

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This theory is also supported by the synthetic analysis performed by the Apollo scientists on lunar rocks during the Apollo expedition. It was found that the moon was made up of lighter elements predominantly found in the Earth’s crust. The material from which the moon was made came from Earth’s crust, leaving the core of the planet intact. After the Image source:

collision of two celestial bodies, the remains of Theia’s core and chunks of Earth’s crust would have centered around the Earth’s ecliptic plane, the path where the moon orbits today.