Five hours: That's how long it might have taken for our Moon to form
Scientists have found that the Moon may have formed within hours after the giant impact that shaped Earth's early history.
The Moon may have come together far faster than scientists once thought.
A new computer simulation suggests Earth’s natural satellite could have formed in about five hours after a gigantic collision between a much younger Earth and a Mars-sized body called Theia.
The finding does not prove that the Moon actually formed on that timescale, but it offers a new way of looking at one of the biggest events in Earth’s early history.
The study, led by Adeene Denton of the Southwest Research Institute with researchers from the University of Arizona, was published in The Astrophysical Journal Letters.
HOW WAS THE MOON CREATED?
The leading explanation behind the formation of the Moon is the giant-impact theory.
Around 4.5 billion years ago, a Mars-sized protoplanet named Theia is thought to have slammed into Earth, and the enormous collision threw material from the two cosmic bodies into orbit.
Scientists have traditionally modelled this material to form a disk around Earth, with the Moon gradually assembling from that debris.
But the new study adds another layer that earlier models largely left out; the strength of the rocks involved.
Hotter rock is weaker and deforms more easily, while colder material can resist the violence of a collision better.
As temperature affects how strong planetary material is, the factor could have played a larger role than we know.
A MOON WITHIN HOURS?
When the researchers included these properties in their simulations, they found that the outcome could change significantly depending on how hot Earth and Theia were when they collided.
In one scenario, using temperature conditions similar to those in the original giant-impact models, an intact Moon-sized body emerged within roughly five hours of the collision.
In other scenarios, a disk of debris remained around Earth and the Moon formed more gradually.
“We discovered that the pre-existing geology of the Mars-sized proto-Moon matters,” Denton said.
The result is something to pay attention to because it connects the Moon’s possible formation process with when the giant impact happened.
A hotter Theia would have behaved differently from a cooler, stronger one.
Nasa said that computer models already show the Moon could have formed within hours after a giant impact, although scientists are still working to determine which formation scenario best matches the evidence preserved in lunar rocks.
In other words, the five-hour Moon is not a proven fact but a result from a computer model, an interesting prospect that could help scientists better understand how Earth’s closest neighbour came into existence.