The Moon Assembled from a Swarm of Earth's Fragments ⚡ экспресс
The multi-impact model explains the formation of the Moon without a single giant collision. It is assumed that a thin pro-satellite disk revolved around the young Earth. Numerous asteroid impacts ejected mantle rocks into this disk. The ejected debris moving in the same direction (prograde) merged with the disk, while the opposite-moving (retrograde) ones fell back. This naturally explains the deficiency of iron on the Moon — Earth's mantle is poor in it. The mechanism resembles merging into a circular flow: particles moving with the flow easily join, while those against it are slowed down.
When countless asteroids pummeled the young Earth, they tore chunks from its mantle. These fragments spiraled in a cosmic disk around the planet and, like a snowball in a blizzard, fused into the Moon.
The same scenario applies to Pluto's moon Charon and hundreds of binary asteroids in the Solar System. Importantly, fragments moving in the same direction as the disk's rotation stayed in orbit and contributed to growth, while those coming the opposite way fell back. Thus, some material destined for the Moon scattered over Earth: we walk on rocks that once traveled through space.
🎯 The Moon is iron-poor, which long didn't fit the single-impact hypothesis: such a collision would have mixed crust and mantle material, enriching the satellite. The new multi-impact model naturally solves this puzzle.