A massive impact immediately placed a 'Moon-like body' into Earth's orbit, reveals new study

The new theory questions conventional theories, including those predicting the Moon evolved within a debris disc around Earth.
Sade Agard
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Moon orbiting Earth

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The Moon's origin can be explained by a giant impact immediately placing a 'Moon-like body' into an orbit around Earth, according to new research published in the Astrophysical Journal Letters today.

This scenario opens up new possibilities for the initial lunar orbit as well as the Moon's expected composition and internal structure. Future lunar missions will likely provide fresh information about the type of massive impact that created the Moon, which will help us understand the history of Earth itself.

Supercomputer simulations aided the new explanation for the Moon's origin

To find scenarios that could explain the current Earth-Moon system, scientists from Durham University's Institute for Computational Cosmology used the most detailed supercomputer simulations. The study conducted hundreds of simulations of collisions which involved altering the mass and spins of the two colliding bodies along with the angle and speed of the crash.

On the DiRAC Memory Intensive service ("COSMA"), offered by Durham University on behalf of the DiRAC High-Performance Computing facility, these computations were carried out using the SWIFT open-source simulation code.

Earlier investigations failed to identify that the Moon's outer layers contain more material from the Earth

The additional computer capacity allowed researchers to identify traits that weren't accessible for earlier investigations. The study proves that lower-resolution simulations can lose out on essential aspects of large-scale collisions. High-resolution simulations could have only created the Moon-like satellite, and the additional information revealed how its outer layers contained more material from the Earth.

"This formation route could help explain the similarity in isotopic composition between the lunar rocks returned by the Apollo astronauts and Earth's mantle," explains co-author Dr. Vincent Eke in a press release. Eke further explains that the thickness of the lunar crust may also have observable effects, which would help us narrow down the specifics of the collision's nature.

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The new theory questions conventional theories, including those predicting the Moon evolved within a debris disc around Earth

Suppose a large portion of the Moon formed shortly after the massive impact. In that case, it may also suggest that less of it melted throughout its formation. This questions conventional theories that predicted that the Moon evolved within a debris disc around Earth. Depending on the specifics of the eventual solidification, these theories could forecast various internal structures for the Moon.

And that's not all. The researchers discovered that even when a satellite passes so near to Earth that it may be ripped apart by 'tidal forces' from Earth's gravity, the satellite can survive and be propelled onto a larger orbit- secure from further destruction.

'It was extra exciting that the new results could include a tantalizingly Moon-like satellite in orbit'

"This opens up a whole new range of possible starting places for the Moon's evolution. We went into this project not knowing exactly what the outcomes of these very high-resolution simulations would be. So, on top of the big eye-opener that standard resolutions can give you wrong answers, it was extra exciting that the new results could include a tantalizingly Moon-like satellite in orbit," adds Dr. Jacob Kegerreis, lead author of the study.

Previous theories about the Moon's origin

The early Earth and a Mars-sized object known as Theia are believed to have collided 4.5 billion years ago, resulting in the formation of the Moon. According to most theories, the Moon was formed over time as the impact's debris accumulated. This has been challenged by studies of lunar rocks, which reveal that their composition is similar to that of the Earth's mantle. At the same time, the collision creates Theia-derived debris primarily.

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