Supercomputer simulation reveals how a giant impact could have shaped the moon

Credit: Durham University

Leading scientists from the Institute for Computational Cosmology at Durham University have used the most detailed supercomputer simulations yet to reveal an alternative explanation for the moon’s origin, 4.5 billion years ago. And revealed the existence of a giant collision between Earth and[{” attribute=””>Mars-sized body could immediately place a Moon-like body into orbit around Earth.

High-end simulations

In their search for scenarios that could explain the present-day Earth-Moon system, the researchers simulated hundreds of different impacts at high resolution, varying the angle and speed of the collision as well as the masses and spins of the two colliding bodies. These calculations were performed using the SWIFT open-source simulation code, run on the DiRAC Memory Intensive service (“COSMA”), hosted by Durham University on behalf of the DiRAC High-Performance Computing facility.

Additional computational power revealed that low-resolution simulations can miss critical aspects of large-scale collisions. Using high-resolution simulations, researchers can discover features that were not accessible in previous studies. Only high-resolution simulations produced the moon-like satellite, and additional details revealed how its outer layers contained more Earth-originated material.

If a large portion of the Moon formed immediately after the giant impact, this could also mean that the melting point of the Moon is lower during formation compared to traditional theories where the Moon grew within the disk of debris around the Earth. Depending on the details of the subsequent solidification, these theories should predict the various internal structures of the Moon.

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

Moreover, they discovered that even when a satellite passes so close to the Earth that it is expected to be torn apart by “tidal forces” from Earth’s gravity, the satellite can actually survive. In fact, it could also be propelled into a wider orbit, safe from future destruction.

A bunch of new possibilities

“This opens up a whole new set of potential springboards for lunar evolution,” said Jacob Kejris, lead author on the study. “We went into this project without knowing exactly what the results of these high-resolution simulations would be. So, in addition to the big opening that standard decisions can To give you wrong answers, it was very exciting that the new findings could include a puzzling, lunar-like satellite in orbit.”

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

This immediate satellite scenario opens up new possibilities for the initial lunar orbit as well as the predicted composition and internal structure of the Moon. This may help explain unsolved mysteries such as the moon’s tilted orbit away from the Earth’s equator; Or it could produce an early moon that is not fully molten, which some scientists suggest could be a better match for its thinner crust.

The next several lunar flights should reveal new clues about the type of giant impact that led to the moon, which in turn will tell us about the history of the Earth itself.

The research team included scientists in[{” attribute=””>NASA Ames Research Centre and the University of Glasgow, UK, and their simulation findings have been published in the Astrophysical Journal Letters.

Reference: “Immediate Origin of the Moon as a Post-impact Satellite” by J. A. Kegerreis, S. Ruiz-Bonilla, V. R. Eke, R. J. Massey, T. D. Sandnes and L. F. A. Teodoro, 4 October 2022, Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ac8d96

The research was partly supported by a DiRAC Director’s Discretionary Time award and a Science and Technology Facilities Council (STFC) grant.

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