A huge impact could have formed the moon faster, scientists show in new simulations

Scientists at Durham University’s Institute for Computational Cosmology used the most detailed supercomputer simulations yet to come up with an alternative explanation for the moon’s origin, with a giant impact immediately launching a lunar-like body into orbit around Earth.

In search of scenarios that could explain today’s Earth-Moon system, the researchers simulated hundreds of different impacts, varying the angle and speed of collision, and the masses and spins of the two colliding bodies. These calculations were performed using the open-source SWIFT simulation code running on the DiRAC Memory Intensive Service (“COSMA”) hosted by Durham University on behalf of the DiRAC High-Performance Computing Facility.

The extra computing power showed that lower-resolution simulations can miss important aspects of large-scale collisions, allowing researchers to discover features that were inaccessible to previous studies. Only the high-resolution simulations produced the lunar-like satellite, and the additional detail showed how its outer layers were richer in material originating from Earth.

If much of the moon formed immediately after the giant’s impact, it could also mean that less was melted during formation than in standard theories, in which the moon grew around the earth in a debris disk. Depending on the details of the subsequent solidification, these theories should predict different internal structures for the moon.

Study co-author Vincent Eke said: “This formation pathway could help explain the similarity in isotopic composition between the lunar rocks brought back by the Apollo astronauts and the Earth’s mantle. There could also be observable consequences for the thickness of the moon’s crust, which would allow us to more accurately determine the nature of the collision that occurred.

In addition, they found that even if a satellite flies so close to Earth that it might be expected to be torn apart by the “tidal forces” of Earth’s gravity, the satellite will, in fact, not only survive but be pushed into a wider orbit can. safe from future destruction.

Lead researcher on the study, Jacob Kegerreis, said: “This opens up a whole range of new possible starting points for the moon’s evolution. We went into this project not knowing exactly what the results of these very high resolution simulations would be. So, in addition to the huge eye-opener that standard resolutions can give you wrong answers, what was particularly exciting was that the new results could include an enticingly moon-like satellite in orbit.

The moon is believed to have formed after a collision 4.5 billion years ago between young Earth and a Mars-sized object called Theia. Most theories create the moon by gradually accumulating debris from this impact. However, this has been challenged by measurements of lunar rocks showing that their composition is similar to that of Earth’s mantle while the impact produces debris mostly from Theia.

This immediate satellite scenario opens up new possibilities for the initial lunar orbit and the predicted composition and internal structure of the moon. The many upcoming lunar missions should provide new clues as to what kind of gigantic impact led to the moon, which in turn will tell us something about the history of Earth itself.

The research team consisted of scientists from NASA Ames Research Center and the University of Glasgow, UK, and their simulation results were published in Astrophysical Journal Letters.