A study published on Oct. 31 in the journal Nature raises a new theory about how the moon was formed. The study claims that the moon was formed by the debris left by a high-energy collision.
Previously, it was assumed that the moon came from a Mars-sized object that collided with other hot, planet-sized objects. The collision eventually turned this into Earth and the mass of debris that got thrown off eventually condensed into the moon. However, further research has raised some questions about this idea.
Scientists used to think that planetary bodies have different isotopic compositions and were formed from different parts of the solar system. However, it turns out that the moon actually contains Earth-like composition. Additionally, if the previous theory is true, this does not explain why the moon is tilted five degrees off the equator instead of orbiting just over it.
Instead, researchers from the University of California, Davis, SETI Institute in Mountain View, California, University of Maryland and Harvard University developed a new model that shed light into this problem. A giant impact left some debris that eventually formed into our planet and the moon, which explains the similarity of their compositions.
The moon then reached a point known as LaPlace plane transition. This flipped our planet upright but it did not affect Earth’s orbit around the sun. Meanwhile, the moon was still orbiting at a high angle to the equator at the same time.
After several tens of millions years, the moon slowly distanced itself from Earth. It eventually reached a second transition point, which is known as the Cassini transition. At this point, the moon’s inclination dropped to around five degrees.
Senior author Sarah Stewart of the University of California, Davis told Space.com,”With a giant impact, the moon forms from a disk around the moon’s equator, and even though the dynamical evolution of the system is complicated, if the moon started near the Earth’s equator, we expect that it should stay near the Earth’s equator as it moves away from the Earth over time — but we instead see this five-degree inclination.”