Simulations reveal how Earth’s moon may have formed
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Researchers at the Southwest Research Institute and the University of Arizona used new computer modeling to study how Earth acquired its unusually large moon.
The team ran simulations of the collision between Earth and a Mars-sized object called Theia approximately 4.5 billion years ago. Unlike earlier studies, these simulations accounted for the strength of the materials making up both Earth and Theia, as well as their temperatures.
The researchers found that the geologic properties of the colliding bodies significantly affected moon formation. Previous models treated Earth and Theia as fluids, assuming the collision was energetic enough to melt and vaporize them. However, Denton and her team discovered that material strength is crucial, especially when studying collisions involving smaller bodies.
Their simulations showed that depending on the temperature of Earth and Theia, the impact could either create a disk of debris from which the moon formed over time, or produce an intact moon within hours. The new work connects the timing of the impact to the moon’s initial state and composition. The simulations suggest that if Earth and Theia were hotter at the time of impact, a debris disk would form.
If they had similar temperatures, an intact moon could emerge relatively quickly. While the similar composition of Earth and the moon remains a puzzle, the researchers propose that both bodies formed from the same region of the solar system, unlike Mars.
