Giant impact and Moon formation: new simulations reveal details

The giant impact theory suggests that the collision of proto-Earth with a Mars-sized planet, called Theia, resulted in the formation of the Moon. This event would have produced an iron-poor debris disk that coalesced to form the natural satellite. A new study revisits this hypothesis using smoothed particle hydrodynamics (SPH) simulations with real strength properties. The research shows that resistance in Theia's outer layer may have altered the transfer of momentum during the collision, influencing the Moon's formation ¹.

The importance of temperature and resistance

The temperature of Theia at the time of impact may have been crucial in determining whether the Moon formed from a debris disk or a solid body. Simulations indicate that a hot but solid Theia could have produced an intact Moon, while a cooler and more resistant Theia could have generated a protolunar disk. These differences arise due to varied mechanical responses as a function of temperature ¹.

The study also highlights that the resistance of Theia's crust may have influenced the impact dynamics, producing a variety of possible outcomes, including the core of a new Moon. The research suggests that the timing of the impact — whether earlier or later — may have determined whether the result was a proto-Moon or a lunar debris disk. An earlier collision with a hot Theia would have a different result than a later collision with a cooler and more solid Theia ².

The new modeling does not definitively resolve the question of how the Moon formed, but it offers an interesting perspective by showing that the debris disk phase may have been completely omitted. This opens new possibilities for understanding the formation of the natural satellite, which is still a mystery to scientists ².