Giant impact could have formed an intact moon within five hours, simulations suggest

New Southwest Research Institute-led modeling suggests that a giant impact between a Mars-sized object and Earth could have formed an intact moon within five hours, based on simulations that account for material strength. These simulations, conducted in collaboration with the University of Arizona, show that when material strength is considered, the moon can form more quickly and remain intact, unlike previous models that ignored strength. The research highlights that the preexisting geology of the Mars-sized proto-moon plays a critical role in how the moon forms from the impact. The study uses advanced computational methods to model the collision dynamics, revealing that hotter bodies are weaker and that temperature affects the outcome of the impact. Some scenarios produce an intact moon within hours, while others result in a protolunar disk that eventually forms the moon over time.

• "Theia" may have impacted Earth to create the moon, but previous models ignored material strength, which was thought to be insignificant for such high-energy events.
• Simulations that incorporate strength show that the moon can form more quickly and remain intact, depending on the temperature of the colliding bodies.
• The study finds that the Earth and Theia's initial thermal state influences whether the moon forms intact or from a protolunar disk.

These findings challenge previous assumptions about the timing and nature of the moon's formation. The research suggests that the moon's current composition and thermal state may be linked to the thermal conditions of the Earth and Theia at the time of the impact. The study also highlights the importance of material strength in determining the final state of the moon, providing new insights into the formation of the Earth-moon system. The research is published in The Astrophysical Journal Letters and is the first to show that material strength and temperature play a central role in moon formation.

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