New supercomputer simulation suggests the Moon may have formed in mere hours, not months or years

New supercomputer simulation suggests the Moon may have formed in mere hours, not months or years

In brief: The Moon is a staple in the night sky, but have you ever stopped to consider how it came to be? Researchers have been asking this question for decades and a new simulation adds an interesting wrinkle to the debate.

One leading theory suggests ancient Earth was hit by an object called Theia that was roughly the size of Mars. It was previously believed that debris from the collision came together in orbit over months or years to create our satellite.

The new simulations were run at the highest resolution of any sim used to study the Moon’s origins and suggest the offshoot could have been forms in a matter of hours after impact. The higher-res sims also surfaced new behaviors and details that simply were not evident with lower resolution models.

Vincent Eke, a researcher at Durham University who helped co-author the study, said the more we learn about how the Moon came to be, the more we discover about the evolution of the Earth. Lunar rock samples have very similar isotopic signatures to rocks here on Earth, suggesting material that makes up the Moon could have originated here.

Theia could have also been isotopically similar to Earth, but it would be an unlikely coincidence. The new simulation provides a plausible explanation as to why the isotopic signatures are so similar and could also explain other quirks like the Moon’s tiled orbit and its thin crust.

Jacob Kegerreis, a postdoctoral researcher at NASA’s Ames Research Center and lead researcher of the study, said the simulations open up a whole new range of possible starting places for the Moon’s evolution. Or, it could just be a hollow, artificial structure brought here by someone else for an unknown purpose.

The team’s paper has been published in The Astrophysical Journal Letters.

NASA said additional analysis of future lunar samples, like those scheduled to be brought back from Artemis missions, will help narrow down which theories about the Moon’s origin are correct.

The Earth and moon have similar makeup

Understanding the moon’s origins requires using what we know about the moon. Our knowledge of its mass, orbit, and the precise analysis of lunar rock samples are key to creating scenarios for what we see today.

Previously prevailing theories could explain some aspects of the moon’s properties quite well, such as its mass and orbit, but with some major caveats. One outstanding mystery has been why the composition of the moon is so similar to Earth’s. Scientists can study the composition of a material based on its isotopic signature. An isotopic signature is a chemical clue to how and where an object formed. The lunar samples scientists have been able to study in labs show very similar isotopic signatures to rocks from Earth, unlike rocks from Mars or elsewhere in the solar system. This makes it likely that much of the moon’s material originally came from Earth.

In previous scenarios, Theia sprayed out into orbit and mixed with only a little material from Earth. These scenarios showed it’s less likely we’d see such strong isotopic similarities. That is, unless Theia was also isotopically similar to Earth, which would be an unlikely coincidence. The new theory uses more Earth material to create the moon, particularly its outer layers, which could help explain the similarity in composition.

There have been other theories proposed to explain these similarities in composition. One is the synestia model. In this model, the moon formed inside a swirl of vaporized rock from the collision. But theories such as these struggle to explain the moon’s current orbit.

A speedier theory of how a collision may have formed the moon

The new faster, single-stage formation theory offers a cleaner and more elegant explanation for both these outstanding issues. Also, it could give new ways to find answers for other unsolved mysteries. This scenario can put the moon into a wide orbit with an interior that isn’t fully molten. And that could potentially explain properties like the moon’s tilted orbit and thin crust. Which is why it’s one of the most enticing explanations for the moon’s origins yet.

Getting closer to confirming which of these theories is correct requires analysis of future lunar samples. This is something NASA’s future Artemis missions can provide. Samples from other parts of the moon and from deeper beneath the moon’s surface will allow scientists to compare how real-world data matches up to these simulated scenarios. In addition, it will help explain how the moon evolved over billions of years.


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