Most theories for the origin of the Moon are that it came from the Earth after a collision with a space object. While such an event will have been cataclysmic in terms of its impact, new research finds the collision may have formed the Moon in mere hours.
This is based on simulations conducted at NASA/Ames Research Center. This models the prevailing theory that the Moon was formed out of the debris of a collision between the Earth and an object about the size of Mars, called Theia. While such an impact probably happened, the latest simulations suggest the Moon formed in a matter of hours as material from the Earth and Theia was flung into orbit on the impact.
Theia is a hypothesized ancient planet in the early years of the Solar System. Based on the ‘giant-impact hypothesis’, Theia collided with the early Earth some 4.5 billion years ago. This means, the Moon may have formed from the ejecta of a collision between Theia and the proto-Earth.
Alternative Moon formation theories are:
- The Moon was spun off from Earth’s molten surface by centrifugal force.
- The Moon was formed elsewhere and was subsequently captured by Earth’s gravitational field.
- The Earth and the Moon formed at the same time and place from the same accretion disk (a structure formed by diffuse material in orbital motion around a massive central body).
A strong piece of evidence is that the composition of the Moon is very similar to Earth’s. The composition of a material assessment is based on its isotopic signature, a chemical clue to how and where an object was created. This suggests that the material that makes up the Moon originally came from Earth.
A video of the simulation can be found here:
However, the most commonly accepted theory is that the Moon formed out of the debris of a collision. This view is strengthened by new simulations, based on the highest resolution. This required input of mass, orbit, and the precise analysis of lunar rock samples. The theory is not atypical since the cosmos is filled with collisions and such impacts are an essential part of how planetary bodies form and evolve.
Creating even more collusive data could be achieved by the analysis of future lunar samples brought back to Earth for study from NASA’s future Artemis missions.
The research appears in The Astrophysical Journal Letters, titled “Origin of the Moon as a Post-impact Satellite.”
