How is the Moon thought to have formed during the Hadean Eon?

During the Hadean Eon, a period characterized by the intense formation and stabilization of the early Earth, the most widely accepted explanation for the Moon's origin is the giant-impact hypothesis.12

According to this theory, shortly after Earth formed from the solar nebula approximately 4.6 billion years ago, it was struck by a Mars-sized body named Theia. This titanic, glancing collision ejected a massive cloud of debris—primarily composed of mantle material from both Earth and the impactor—into orbit around the planet. This material eventually aggregated to form the Moon.12

This model is favored because it accounts for several key observations:
* Composition: The Moon is significantly depleted in iron compared to Earth, as the ejected material was primarily derived from the mantles of the colliding bodies.1
* Dynamics: Computer simulations demonstrate that such an impact could produce an orbiting debris disk with sufficient mass to form the Moon.1
* Evolution: The intense heat generated by the collision explains the Moon's initial depletion of volatile elements.1

Other historical theories, such as coaccretion, fission, and capture, have largely fallen out of favor due to their inability to reconcile the physical and chemical properties of the Earth-Moon system.31