Once a leading theory of the origin of the Earth-Moon system, the Capture Theory possessed the virtues of simplicity and intuitive plausibility. The numerous instances of moons with retrograde orbits supported it. The lunar orbit’s three moments of inertia were consistent with a past very eccentric orbit, which fit a capture1. However, the Moon would have had to come from a different part of the solar system to account for its very depleted iron compared to the Earth’s iron, which meant that it would approach the Earth at a high velocity that would prevent capture. Researchers searched in vain for a braking mechanism that would slow it down so it could be captured. Still, the accumulated evidence and arguments made the Capture Theory a viable one.
But