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One side of the moon is riddled with far more craters than the other, and researchers finally know why: A massive asteroid that smashed into the moon about 4.3 billion years ago wreaked havoc in the moon’s mantle, according to a new study.
More than 9,000 visible holes cause a hole in moonthanks to a barrage of collisions from meteorites, asteroids and comets over billions of years, according to International Astronomical Union (Opens in a new tab). However, these craters are not evenly distributed across the surface of the Moon. The far side of the moon that people never see Land Because the Moon is gradual (meaning it takes the same amount of time for the Moon to orbit and revolve around the Earth), its focus is much greater on craters than on the visible near side.
The near part of the Moon has fewer craters because the surface is covered in lunar maria – vast areas of solid lava that we can see with the naked eye on Earth as dark spots on the Moon. These lava fields likely covered craters that would otherwise be near the Moon. The far side of the Moon has almost no lunar maria, which is why the craters of the Moon are still visible.
Scientists have long suspected that lunar Maria formed in the aftermath of a massive collision about 4.3 billion years ago. This collision created the Antarctic-Aitken Basin (SPA), a massive crater with a maximum width of about 1,600 miles (2,574 kilometers) and a maximum depth of 5.1 miles (8.2 kilometers), the largest crater on the Moon and the second largest confirmed impact crater. at Solar System. However, until now researchers have not been able to explain why lava fields are found only on the near side of the Moon.
The new study found that the SPA effect created a unique phenomenon within the moon’s mantle, the layer of magma below the crust, that only affected the near side.
“We know that large impacts like the one that formed the SPA will create a lot of heat,” said lead author Matt Jones, a PhD student in planetary sciences at Brown University, He said in a statement (Opens in a new tab). The question is how this temperature affects the internal dynamics of the Moon.
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Researchers already knew that near-Earth lava fields originated inside the lunar mantle, because lunar samples brought in by the Apollo missions contain radioactive and heat-generating elements such as potassium, phosphorous and thorium, which are suspected to be abundant within the lunar mantle, according to the statement.
In the new study, computer simulations revealed that the SPA effect would have created a heat plume within the mantle that would push the radioactive elements toward the crust. The researchers repeated the simulations for a number of possible scenarios for the SPA impact, including direct hits and lightning strikes, and found that no matter how the asteroid impacted, the mantle impact would only affect the near side of the Moon.
In other words, when a space rock collided with the moon, it caused lava to flow out of the mantle on the near side, burying many ancient impact craters.
“What we are showing is that under any reasonable conditions at the time of SPA formation, these heat-producing elements end up being concentrated on the near side,” Jones said. “We speculate that this contributed to the mantle melting that led to the pyroclastic flows we see at the surface.”
The statement said the researchers were pleased to have solved what they described as “one of the most important questions in lunar science.”
“The impact of SPA is one of the most important events in the history of the Moon,” Jones said. He added that being able to better understand how it formed the sides of the moon we see today is “really exciting.”
The study was published online April 8 in the journal science progress (Opens in a new tab).
Originally published on Live Science.
Editor’s note: This story was updated at 12:15 PM EDT to correct the description of the tidal lock.
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