The Moon Assembled from a Swarm of Earth's Fragments ⚡ экспресс
The multi-impact model offers a mechanism for the formation of the Moon, Charon, and binary asteroids without catastrophic collisions. It is based on the existence of a low-mass prograde protosatellite disk around proto-Earth. Lunar material was ejected from Earth's mantle by numerous large asteroid impacts, which explains the iron deficiency in lunar rocks. Collisions of the ejected debris with particles of the prograde disk stabilize them into satellite orbits. The high efficiency of the mechanism is demonstrated: prograde ejecta easily merge with the disk, while retrograde material falls back to Earth. Such a model resolves contradictions of the giant impact hypothesis and extends to the formation of other moons.
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.