Scientists from Durham University’s Institute for Computational Cosmology have used the most detailed supercomputer simulations to date to uncover an alternative explanation for the origin of the Moon, in which a giant impact put a Moon-like body in orbit around Earth.
Scientists from Durham University’s Institute for Computational Cosmology have used the most detailed supercomputer simulations to date to uncover an alternative explanation for the origin of the Moon, in which a giant impact put a Moon-like body in orbit around Earth.
The researchers simulated hundreds of different impacts, changing the angle and speed of the collision as well as the masses and rotations of the two colliding bodies in their search for scenarios that could explain today’s Earth-Moon system. These calculations are performed using the open-source simulation software SWIFT, which runs on the high-memory COSMA service at Durham University.
The added computational power revealed that the lower-resolution simulations could miss important aspects of large-scale collisions, allowing the researchers to discover features inaccessible to previous studies. Only the high-resolution imaging created the moon-like satellite, and the extra detail showed how its outer layers were rich in Earth-derived material.
If a large part of the moon was formed immediately after the giant impact, it could also mean that a smaller part was melted during the formation compared to the usual theories according to which the moon developed in a debris disk around the earth. Depending on the details of the subsequent solidification, these theories would predict different internal structures of the moon.
Vincent Eick, co-author of the study, said: “This formation pathway could explain the similarity in the isotopic composition between the lunar rocks returned by the Apollo astronauts and the Earth’s mantle. There may also be observable results in the thickness of the lunar crust, which will allow us to more precisely identify the type of collision that occurred “.
In addition, they found that even when a satellite passes so close to Earth that it would be expected to be torn apart by “tidal forces” from Earth’s gravity, the satellite can actually not only survive but also be pushed into a wider orbit, where it will be safe from future destruction.
Jacob Kagris, the lead researcher of the study, said: “This opens up a whole new field of possible places where the Moon began to evolve. We went into this project not knowing exactly what the results of these high-resolution imaging would be. So in addition to the great illumination that the usual resolutions can provide answers errors, it was especially exciting that the new results could include a tempting moon-like satellite in orbit.”
The moon is thought to have formed after a collision 4.5 billion years ago between the young Earth and a Mars-sized object called Thea. In most theories the moon was formed by the gradual accumulation of the fragments from this impact. But measurements of the lunar rocks – which showed that their composition is similar to the composition of the Earth’s mantle, while the impact creates fragments that come mainly from Thea – cast doubt on this.
This scenario of an instant satellite opens up new possibilities about the Moon’s initial orbit and also its predicted interior composition and structure. The many upcoming lunar missions will reveal new clues about the type of giant impact that led to the moon, and from it we will learn about the history of Earth itself.
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