Supercomputer simulations reveal how a giant impact could have formed the Moon

Credit: Durham University

Pioneering scientists at Durham University’s Institute for Computational Cosmology have used the most detailed supercomputer simulations to date to reveal an alternative explanation for the origin of the Moon 4.5 billion years ago. years. It revealed that a giant impact between Earth and a[{” 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.

The extra computing power revealed that low-resolution simulations can miss crucial aspects of large-scale collisions. With high-resolution simulations, researchers can uncover features that weren’t accessible in previous studies. Only the high-resolution simulations produced the Moon-like satellite, and the additional details revealed how its outer layers contained more material from Earth.

If much of the Moon formed immediately after the giant impact, it could also mean that less melted during formation than in traditional theories where the Moon grew into a disk of debris around Earth. . Depending on the details of later 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 lunar rocks returned by Apollo astronauts and the Earth’s mantle. It may also be there. have observable consequences on the thickness of the lunar crust, which would allow us to better understand the type of collision that took place.

What’s more, they found that even when a satellite passes so close to Earth that one would expect it to be torn apart by the “tidal forces” of Earth’s gravity, the satellite can actually survive. . In fact, it can also be pushed into a wider orbit, safe from future destruction.

A range of new possibilities

Jacob Kegerreis, lead researcher on the study, said: “This opens up a whole new range of possible starting points for the evolution of the Moon. We embarked on this project without knowing exactly what the results of these very high resolution simulations would be. So, in addition to the big reveal that standard resolutions can give you the wrong answers, it was very exciting that the new results could include an orbiting satellite resembling the Moon.

The Moon is believed to have formed after young Earth collided with a Mars-sized object called Theia 4.5 billion years ago. Most theories build the Moon by a gradual accumulation of debris from this impact. However, this has been disputed by measurements of lunar rocks showing that they are similar in composition to the Earth’s mantle, while the impact produces debris that comes mainly 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. It could help explain unsolved mysteries like the Moon’s tilted orbit away from Earth’s equator; or could produce an early moon that is not completely melted, which some scientists believe may better match its thin crust.

The many lunar missions to come 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 from[{” attribute=””>NASA Ames Research Centre and the 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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