This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: New Southwest Research Institute (SwRI) modeling, conducted in collaboration with scientists at the University of Arizona, shows fundamental differences in how the moon may have formed from the giant impact that created the Earth–moon system. The new results used state-of-the-art computational techniques that factor in the material strength of the two colliding planets.
These impact simulations could change how researchers understand moon formation and may help constrain the timing of the event. The research is published in The Astrophysical Journal Letters. "We discovered that the preexisting geology of the Mars-sized proto-moon matters," said Dr.
Adeene Denton, formerly a NASA Postdoctoral Program fellow at SwRI and now a postdoctoral researcher in SwRI's Solar System Science and Exploration Division. "When you simulate the Earth and the moon as colliding bodies with geologic properties, it changes how the moon forms out of that impact—that's something we considered unnecessary before." Earlier studies of the giant impact scenario included a foundational 2001 paper by Dr. Robin Canup, vice president of SwRI's Solar System Science and Exploration Division in Boulder, Colorado, and Dr.
Erik Asphaug, a professor at the University of Arizona and co-author of the current study. That research found that a Mars-sized object, Theia, may have smashed into Earth to create the Earth–moon system, but those simulations and subsequent giant impact modeling ignored material strength, which was thought to be insignificant for such high-energy events. Denton and her team revisited this hypothesis, using modern computational methods that incorporate temperature-dependent geologic strength for the first time.
"Models have evolved to include material strength, something that's really important when you're studying collisions between smaller bodies like asteroids or for my previous paper about the formation of the Pluto-Charon system," Denton said. "We weren't sure if it would matter for the moon or not. When we did the simulations, we found it actually matters quite a bit." Hotter bodies are weaker than colder ones, and the team found that moon formation is sensitive to the temperatures of the colliding bodies.
Some scenarios produce a fully intact moon within hours of the impact, while others produce a protolunar disk around Earth that ultimately forms the moon over time. Because protoplanets generally start hot and cool with age, this establishes an important new connection between the timing of the giant impact and the nature of the moon's initial state and assembly. "Depending on how hot the Earth and Theia are prior to the collision, the impact can destroy Theia and produce this massive disk of debris that eventually forms the moon," Denton said.
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