Earth’s moon could have taken only hours to form from a shattered mess: ScienceAlert

The Moon could have formed immediately after a cataclysmic impact that ripped off a piece of Earth and hurled it into space, according to a new study.

Since the mid-1970s, astronomers have thought that the Moon could have been formed by a collision between Earth and an ancient Mars-sized protoplanet called Theia. the colossal impact would have created a vast debris field from which our lunar companion slowly formed over thousands of years.

But a new hypothesis, based on supercomputer simulations done at a higher resolution than ever before, suggests that the formation of the Moon may not have been a slow and gradual process after all, but one that took place over just a few hours.

The scientists published their findings on October 4 in the journal The Astrophysical Journal Letters.

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“What we’ve learned is that it’s very difficult to predict how much resolution you need to reliably simulate these violent and complex conflicts – you just have to keep testing until you find that further increasing the resolution stops making a difference to your response.” , Jacob Kegerreis, a computational cosmologist at Durham University in England, told Live Science.

Scientists got their first clues about the creation of the Moon after the Apollo 11 mission returned in July 1969, when NASA astronauts Neil Armstrong and Buzz Aldrin brought back 47.6 pounds (21.6 kg) of lunar rock and dust. on earth.

The samples date back to about 4.5 billion years ago, placing the creation of the Moon in the turbulent period about 150 million years after the formation of the solar system.

Other evidence suggests that our largest natural satellite was born from a violent collision between Earth and a hypothetical planet, which scientists named after the mythical Greek Titan Theia – the mother of the Moon, goddess of the Moon.

This evidence includes similarities in the composition of lunar and terrestrial rocks. The Earth’s rotation and the Moon’s orbit have similar orientations. the high combined angular momentum of the two bodies. and the existence of debris disks elsewhere in our solar system.

But exactly how the cosmic collision happened is up for debate. The conventional hypothesis suggests that as Theia crashed into Earth, the planet-shattering impact shattered Theia into millions of pieces, leaving it as floating debris.

The shattered remains of Theia, along with some vaporized rock and gas ripped from our young planet’s mantle, slowly mixed into a disk around which the Moon’s molten sphere coalesced and cooled over millions of years.

However, some parts of the picture remain elusive. An important question is why, if the Moon is made mostly of Theia, do many of its rocks bear striking similarities to those found on Earth?

Some scientists have suggested that more of Earth’s vaporized rocks led to the creation of the Moon than the pulverized remains of Theia, but this idea presents its own problems, such as why other models suggest that a Moon composed mostly of dissolved Earth rocks would have a very different trajectory than what we see today.

To explore different possible scenarios for the formation of the Moon after the collision, the authors of the new study turned to a computer program called SPH With Inter-dependent Fine-grained Tasking (SWIFT), which is designed to closely simulate the complex and continuously changing web of gravity. and hydrodynamic forces acting on large amounts of matter.

This is precisely no simple computational task, so the scientists used a supercomputer to run the program: a system nicknamed COSMA (short for “cosmology machine”) at Durham University’s Distributed Research Utilizing Advanced Computing Facility (DiRAC).

By using COSMA to simulate hundreds of Earth-God collisions at different angles, rotations and speeds, lunar sleuths were able to model the aftermath of the astronomical collision at higher resolutions than ever before.

Resolutions in these simulations are defined by the number of particles the simulation uses. According to Kegerreis, for giant impacts the typical simulation resolution is usually between 100,000 and 1 million particles, but in the new study, he and his fellow researchers were able to model up to 100 million particles.

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“With higher resolution we can study more details – like how a larger telescope allows you to take higher resolution images of distant planets or galaxies to discover new details,” Kegerreis said.

“Secondly, perhaps even more importantly, using too low a resolution in a simulation can give you misleading or even just wrong answers,” he added.

“You can imagine that if you build a car model out of toy blocks to simulate how the car might break in a crash, then if you only use a few dozen blocks, it might just split perfectly in half. But with a few thousand or millions, then you can start crumpling it and it breaks in a more realistic way.”

The higher-resolution simulation left the researchers with a Moon that formed within hours from ejected pieces of Earth and shattered pieces of Theia, offering a one-stage formation theory that offered a clean and elegant answer to the Moon’s visible properties. such as its broad, sloping orbit. Its partially molten interior. and its thin crust.

However, researchers will need to examine samples of rock and dust excavated from deep beneath the Moon’s surface – a target of future NASA Artemis missions – before they can confirm how mixed its mantle might be.

“Even more samples from the lunar surface could be extremely useful for new and more confident discoveries about the composition and evolution of the Moon, which we can then feed back into model simulations like ours,” Kegerreis said. .

“Missions and studies like these and many others are steadily helping us rule out more possibilities and narrow down the true history of both the Moon and Earth, and learn more about how planets form throughout and beyond our solar system. .”

Such investigations could also shed light on how Earth formed and became a life-supporting planet.

“The more we learn about how the Moon formed, the more we discover about the evolution of our own Earth,” said study co-author Vincent Eke, associate professor of physics at Durham University. “Their stories are intertwined – and could be repeated in the stories of other planets changed by similar or very different collisions.”

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This article was originally published by Live Science. Read the original article here.

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