How exactly did our Moon form? About 4.45 billion years ago, 150 million years after the solar system formed, Earth was hit by a Mars-sized object called Thea. The collision of the hypothetical planet Tea of the early solar system might not have had anything to do with the formation of the Moon, suggests a new study published in The Astrophysical Journal Letters.
The cosmos is full of collisions: impacts are an essential part of how planetary bodies form and evolve. Since the 1970s, astronomers have suspected that the moon was created when a giant protoplanet called Tea hit Earth, but research, which has gone on for decades, has never been conclusive. This model has been challenged by looking at the geological composition of the Moon’s surface. The lunar rocks that returned from the Apollo mission have an isotopic composition similar to that of the Earth’s mantle. However, simulations of the Tea collision suggest that such an impact would cause most of the debris to originate from Tea, not Earth. The result is that the theory is inconsistent.
However, a team of researchers from the University of Durham affirms in their new work that the colossal impact immediately placed the moon in orbit around the Earth and was not a gradual process resulting from the cloud of debris that ended up creating a satellite ( our natural satellite).
A new simulation presents an alternative theory: The Moon could have formed immediately, even in a matter of hours, when material from Earth and Tea were thrown directly into orbit after the impact.
The team used open source simulation code to run hundreds of different impact scenarios. Specifically, the simulations used were run using open source SWIFT code carried out on the DiRAC ( Distributed Research Utilizing Advanced Computing ) ( “COSMA”) memory-intensive service, hosted by Durham University. on behalf of the DiRAC high-performance computing facility. By altering the angle, speed, masses, and rotations of the two objects, they looked at the scenarios that best fit our satellite’s formation history, and concluded that the immediate formation after a large collision could be the most likely.
“This formation pathway could help explain the similarity in isotopic composition between moon rocks returned by Apollo astronauts and Earth’s mantle. There may also be observable consequences for the thickness of the lunar crust, which would allow us to further pinpoint the type of collision that took place,” said Vincent Eke, an expert in Computational Cosmology at Durham.
“This opens up a whole new range of possible starting points for the evolution of the Moon,” explained Jacob Kegerreis, a postdoctoral researcher at NASA Ames Research Center in Silicon Valley, California, and lead author of the paper. “We started this project not knowing exactly what the results of these high-resolution simulations would be. So, in addition to the big reveal that standard resolutions can give us misleading answers, it was very exciting that the new results could include a tantalizing satellite similar to the Moon in orbit .”
The researchers hope the findings will encourage more research into the Moon’s composition and internal structure. “The many upcoming lunar missions should reveal new clues about what kind of giant impact drove the Moon, which in turn will tell us about Earth’s history,” the researchers concluded.
Reference: Kegerreis JA, Ruiz-Bonilla S, Eke VR, Massey RJ, Sandnes TD, Theodore LFA. Immediate Origin of the Moon as a Post-impact Satellite. The Astrophysical Journal Letters, 2022; 937(2):L40 DOI:10.3847/2041-8213/ac8d96