- 3705 - MOON - how did the Moon form? How did the Earth take shape and became a life-harboring planet. The more we learn about how the Moon too shape, the more we discover about the evolution of our own Earth. Their histories are intertwined and could be echoed in the stories of other planets changed by similar or very different collisions.
--------------------- 3705 - MOON - how did the Moon form?
- The moon could have formed after a cataclysmic impact that tore off a chunk of Earth and hurled it into space.
Since the mid-1970s, astronomers have thought that the moon could have been made by a collision between Earth and an ancient Mars-size protoplanet called “Theia“. The colossal impact of Theia would have created an enormous debris field from which our lunar moon slowly formed over thousands of years.
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- A new hypothesis, based on supercomputer simulations made at a higher resolution than ever before, suggests that the moon's formation might not have been a slow and gradual process, but one that instead took place within just a few hours.
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- Scientists got their first clues about the moon's creation after the return of the “Apollo 11” mission in July, 1969, when NASA astronauts Neil Armstrong and Buzz Aldrin brought 47.6 pounds of lunar rock and dust back to Earth. The samples dated to around 4.5 billion years ago, placing the moon's creation in the turbulent period roughly 150 million years after the formation of the solar system.
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- Other clues point to our largest natural satellite being birthed by a violent collision between Earth and a hypothetical planet. This evidence includes similarities in the composition of lunar and Earth rocks; Earth's spin and the moon's orbit having similar orientations; the high combined angular momentum of the two bodies; and the existence of debris disks elsewhere in our solar system.
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- But exactly how the cosmic collision played out is up for debate. The conventional hypothesis suggests that as Theia crashed into Earth, the planet-busting impact shattered Theia into millions of pieces, reducing it to floating rubble. Theia's broken remains, along with some vaporized rocks and gas ripped from our young planet's mantle, slowly mingled into a disk around which the molten sphere of the moon coalesced and cooled over millions of years.
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- One outstanding question is why, if the moon is mostly made out 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 went into creating the moon than Theia's pulverized remnants did, but this idea presents its own problems, such as why other models suggest that a moon made mostly of disintegrated Earth rocks would have a vastly different orbit than the one we see today.
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- To investigate different possible scenarios for moon formation following the collision, the new study's authors turned to a computer program called “SPH” With Inter-dependent Fine-grained Tasking “SWIFT“, which is designed to closely simulate the complex and ever-changing web of gravitational and hydrodynamic forces that act upon large amounts of matter.
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- Doing so accurately is no simple computational task, so the scientists used a supercomputer to run the program: a system nicknamed “COSMA” (short for "cosmology machine").
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- By using COSMA to simulate hundreds of Earth-Theia collisions with different angles, spins and speeds, the scientists were able to model the aftermath of the astronomical crack-up at higher resolutions than ever before. Resolutions in these simulations are set by the number of particles the simulation uses. For gigantic impacts the standard simulation resolution is usually between 100,000 and 1 million particles, but the new study was able to model up to 100 million particles.
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- The higher-resolution simulation showed a moon which formed in a matter of hours from the ejected chunks of Earth and the shattered pieces of Theia. The formation theory provided a clean and elegant answer to the moon's visible properties, such as its wide, tilted orbit; its partially molten interior; and its thin crust.
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- Even more samples from the surface of the moon could be extremely helpful for making new and more confident discoveries about the moon's composition and evolution, which we can then trace back to these model simulations like ours.
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- Such investigations could also shed light on how Earth took shape and became a life-harboring planet. The more we learn about how the Moon came to be, the more we discover about the evolution of our own Earth. Their histories are intertwined and could be echoed in the stories of other planets changed by similar or very different collisions.
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October 12, 2022 MOON - how did the Moon form? 3705
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