The Moon may have formed within five hours, U.S. scientists say

The Moon may have taken shape in just five hours after a massive collision rocked the early solar system about 4.5 billion years ago, according to U.S. scientists.

For decades, experts have believed that a Mars-sized planet called Theia struck the young Earth, sending large amounts of molten rock into space. That material was thought to have gradually come together over years before forming Earth’s natural satellite.

Researchers from the Southwest Research Institute and the University of Arizona have proposed another possibility. Using high-powered computer simulations, they found that under some conditions, a largely intact Moon could form very quickly after the impact.

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It all depends on how hot Earth and Theia were before the collision. The impact could destroy Theia and produce a large debris disk that eventually forms the Moon.

Planetary scientist Dr. Adeene Denton of the Southwest Research Institute said the result depended on how hot Earth and Theia were before the collision. A hotter impact could destroy Theia and create a large debris disk that eventually forms the Moon. But when the researchers used the same parameters and temperature structure as in the original collision modelling, the simulation produced an intact Moon in about five hours.

Published in Astrophysical Journal Letters, the findings could help address questions about when the Moon-forming collision occurred. They may also shed light on unresolved features of the Moon, including differences in its composition and the amount of volatile material it contains.

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However, when I used the same parameters as in the original collision modelling, including the same temperature structure, an intact Moon formed within about five hours.