Mar 18, 2025 08:15 PM
(This post was last modified: Mar 18, 2025 09:22 PM by C C.)
https://www.space.com/the-universe/moon/...act-theory
EXCERPTS: The moon is weird. It's completely unlike anything else in the solar system. So how did our planet end up with such a special moon? The answer is that, surprisingly enough, the moon is a piece of our planet. [...] The moon is full of "KREEPs" – that is, potassium (K), rare-Earth elements (REE) and phosphorus (P). These elements don't usually like to hang out together, but lunar samples show that they are often mixed. That requires the moon to have been molten at some point, which takes a lot of energy.
[...] The leading explanation for all of these mysteries is known as the giant impact hypothesis. According to this story, when the solar system was just getting started, a Mars-size protoplanet named Theia slammed into the proto-Earth.
[...] the general picture is that some stuff went flying away, never to return. Other stuff rained onto Earth's surface. And a big chunk remained in orbit. In as little as a few hours — or perhaps up to a century or more — that material coalesced into its own solid object: the moon.
Some models suggest that a second moon, just a few hundred kilometers across, formed past the far side and then slowly approached the moon and pancaked itself. This would explain why the far side of the moon is lumpier than the near side.
[...] As with all hypotheses, it's not perfect. For example, if there's enough energy to liquefy the moon, there's enough energy to liquefy Earth's surface. But there is no evidence for large-scale magma seas in Earth's history. Also, the moon does have some volatile elements, like water, trapped in rock — but a giant-impact, giant-energy event should have gotten rid of those.
Despite those caveats, the giant impact hypothesis is the most compelling story we have for how the moon formed... (MORE - missing details)
https://youtu.be/MG6oUDl0GLk
https://www.youtube-nocookie.com/embed/MG6oUDl0GLk
EXCERPTS: The moon is weird. It's completely unlike anything else in the solar system. So how did our planet end up with such a special moon? The answer is that, surprisingly enough, the moon is a piece of our planet. [...] The moon is full of "KREEPs" – that is, potassium (K), rare-Earth elements (REE) and phosphorus (P). These elements don't usually like to hang out together, but lunar samples show that they are often mixed. That requires the moon to have been molten at some point, which takes a lot of energy.
[...] The leading explanation for all of these mysteries is known as the giant impact hypothesis. According to this story, when the solar system was just getting started, a Mars-size protoplanet named Theia slammed into the proto-Earth.
[...] the general picture is that some stuff went flying away, never to return. Other stuff rained onto Earth's surface. And a big chunk remained in orbit. In as little as a few hours — or perhaps up to a century or more — that material coalesced into its own solid object: the moon.
Some models suggest that a second moon, just a few hundred kilometers across, formed past the far side and then slowly approached the moon and pancaked itself. This would explain why the far side of the moon is lumpier than the near side.
[...] As with all hypotheses, it's not perfect. For example, if there's enough energy to liquefy the moon, there's enough energy to liquefy Earth's surface. But there is no evidence for large-scale magma seas in Earth's history. Also, the moon does have some volatile elements, like water, trapped in rock — but a giant-impact, giant-energy event should have gotten rid of those.
Despite those caveats, the giant impact hypothesis is the most compelling story we have for how the moon formed... (MORE - missing details)
https://youtu.be/MG6oUDl0GLk