Link to [the science release](https://www.swri.org/newsroom/press-releases/swri-led-modeling-identifies-new-scenarios-moon-formation) on the Southwest Research Institute website





New computer simulations suggest the Moon could have snapped into existence almost immediately after a giant collision — or taken far longer, depending on how hot the two crashing worlds were.



Researchers at Southwest Research Institute, working with scientists at the University of Arizona, modeled the ancient smash-up between Earth and a Mars-sized body called Theia. Their work appears in The Astrophysical Journal Letters.



Earlier models of that collision left out one detail: the strength of the rock itself. Scientists assumed the impact was so violent that rock strength wouldn't matter. It does, according to lead author Dr. Adeene Denton, who said the simulations showed the effect is considerable.



Because hot rock is weaker than cold rock, the starting temperature of the two bodies changed the outcome dramatically. In some runs, Theia was torn apart and its debris spread into a ring around Earth that slowly gathered into the Moon. In others, a complete Moon appeared within about five hours.



That matters for dating the event. Young planets start out hot and cool as they age, so the Moon's makeup may point to exactly when the crash happened.



One puzzle remains: Earth and the Moon are made of nearly identical material. Denton's explanation is that Earth and Theia formed in the same part of the young solar system. Earth and Mars are siblings, she said, while Earth and the Moon are closer to fraternal twins.

The Moon May Have Formed in Hours, Not Centuries