The moon could have formed immediately after a cataclysmic impact ripped off a chunk of Earth and hurled it into space, according to a new study.
Since the mid-1970s, astronomers have believed that the moon could have been caused by a collision between Earth and a former March– size protoplanet called Theia; the colossal impact would have created a massive debris field from which our lunar companion slowly formed over thousands of years.
But a new hypothesis, based on supercomputer simulations run at higher resolution than ever before, suggests that the moon’s formation may not have been a slow, gradual process after all, but that it did. rather unfolded in just a few hours. The scientists published their findings Oct. 4 in the journal Letters from the Astrophysical Journal.
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“What we’ve learned is that it’s very difficult to predict the resolution you need to reliably simulate these violent and complex collisions – you just have to keep testing until you see that the “Increasing the resolution no longer makes a difference to the response you get,” Jacob Kegerreis, a computational cosmologist at Durham University in England, told Live Science.
Scientists got their first clues about the moon’s creation after the Apollo 11 mission returned in July 1969, when NASA astronauts Neil Armstrong and Buzz Aldrin brought 47.6 pounds (21.6 kilograms) back to Earth. of lunar rock and dust. The samples dated to about 4.5 billion years ago, placing the moon’s creation in the turbulent period about 150 million years after the formation of the solar system.
Other clues indicate that our largest natural satellite was born from a violent collision between Earth and a hypothetical planet, which scientists have named after the mythical Greek titan Theia – the mother of moon goddess Selene. This evidence includes similarities in the composition of lunar and terrestrial rocks; The rotation of the Earth and the orbit of the Moon having 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 unfolded is up for debate. The conventional hypothesis suggests that when Theia crashed on Earth, the impact of the planet’s destruction shattered Theia into millions of pieces, reducing her to floating rubble. The shattered remains of Theia, along with vaporized rocks and gas extracted from our young planet’s mantle, slowly mixed into a disk around which the moon’s molten sphere coalesced and cooled for millions of years.
Yet some parts of the painting remain elusive. A lingering question is why, if the moon is mostly Theia, do many of its rocks bear striking similarities to those found on Earth? Some scientists have suggested that more pulverized rock from Earth was used to create 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 rock disintegrated Earths would have a very different orbit. than the one we see today.
To investigate 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 network complex and constantly changing gravitational gravity. and hydrodynamic forces that act on large amounts of matter. Doing this with precision is not a simple computational task, so the scientists used a supercomputer to run the program: a system dubbed COSMA (short for “cosmology machine”) at the Distributed Research Utilizing Advanced Computing facility. (DiRAC) from Durham University.
By using COSMA to simulate hundreds of Earth-Theia collisions with different angles, rotations and speeds, lunar sleuths were able to model the aftermath of the astronomical fissure at higher resolutions than ever before. The resolutions of these simulations are defined by the number of particles used by the simulation. According to Kegerreis, for gigantic impacts, the standard 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.
“With higher resolution, we can study more detail – much like how a larger telescope allows you to take higher resolution images of distant planets or galaxies to uncover new details,” Kegerreis said.
“Second, perhaps more importantly, using too low a resolution in a simulation can give you misleading or even just plain wrong answers,” he added. “You can imagine that if you build a model car out of toy blocks to simulate how the car might break in an accident, then if you only use a few dozen blocks, it might splits perfectly in the middle. But with a few thousand or a million, then you might start crumpling it and breaking it more realistically.”
The higher-resolution simulation left researchers with a moon that formed in hours from the ejected chunks of Earth and shattered pieces of Theia, providing a one-step formation theory that offered a clean answer and elegant with visible properties of the moon, such as its wide and inclined orbit; its partially melted interior; and its fine crust.
However, researchers will need to examine samples of rock and dust extracted from deep within the moon’s surface – a goal of NASA’s future Artemis missions – before they can confirm how mixed its mantle might be.
“Even more samples of the moon’s surface could be extremely useful in making new, more certain discoveries about the composition and evolution of the moon, which we can then trace back to model simulations like ours,” said said Kegerreis. “Missions and studies like these and many others regularly help us rule out more possibilities and focus on the real history of the Moon and Earth, and learn more about how planets are forming across and beyond our solar system.”
Such investigations could also shed light on how Earth took shape and became a life-sustaining planet.
“The more we learn about the birth of the Moon, the more we discover about the evolution of our own Earth,” said study co-author Vincent Eke, associate professor of physics at Durham University. said in a press release. “Their histories are intertwined – and could find an echo in the histories of other planets altered by similar or very different collisions.”