A new supercomputer simulation shows that our Moon could have formed within hours of a collision between a proto-Earth and a Mars-sized planet early in the solar system’s history.
The subject of where the Moon came from is something scientists have wrestled with for decades.
Originally it was thought that the Earth and Moon had formed as a double-planet or that the Moon had been gravitationally captured by the Earth as it passed by in the early solar system.
A third hypothesis, known as the fission theory, proposed that the early Earth was spinning so fast that it spun off a lump of itself which became the Moon.
One of the problems with the various Moon formation theories is the size of the Moon in relation to Earth.
It’s very large as moons go where rocky planets are concerned.
And, following analysis of the samples returned from the Moon by the Apollo missions, it was found the that Moon is mostly made of the same stuff as Earth.
The chemicals and isotopes of both bodies are too similar for the Moon to have formed elsewhere in the solar system and wandered by Earth sometime later, only to be captured.
The most recent theory was that a Mars-sized object named Theia hit a then smaller proto-Earth with a glancing blow, liquidizing both bodies and throwing off material that originally formed a ring around the planet and then over tens or hundreds of years would eventually coalesce into the Moon we know today.
Most of Theia and proto-Earth would have become merged and mixed to become planet Earth as we know it.
Some material thrown off in the collision would have fallen back onto the planet with the remainder coming together to form the Moon.
There were always some issues with this hypothesis and computers of the day were not powerful enough to provide an accurate simulation of what that collision looked like.
Now that hurdle has been crossed with the latest supercomputer simulation which suggests that the ring theory is wrong and that the Moon could have formed in a matter of hours:
The simulation was developed by researchers from NASA and the Institute for Computational Cosmology’s Planetary Giant Impact group and Durham University in the U.K.
Several parameters were tested, such as the angle of attack, speed of the impact and whether Theia was spinning or not.
The scenario this detailed model predicts that gives rise to the moon as it is today, starts with Theia hitting the proto-Earth with a glancing blow, blending together with the proto-Earth.
After that, the “splash” from the impact sends a giant blob into orbit that wobbled like jelly, with a smaller blob breaking off.
The larger piece was drawn back into the Earth by gravity, while the smaller was thrown far enough away to remain in orbit and become the Moon.
It is hard to believe that the peaceful orb shining in our night skies had such a violent beginning.
But that is the history of all planets and moons in our solar system as they banged and crashed into each other inside a giant primordial cloud of gas and dust.
Rings of dust and gas have been spotted around other stars in our galaxy, with evidence of collisions happening in them.
We can only imagine the violence taking place there and the strange new worlds that might emerge.
