Artist’s conception of hot, molten Moon emerging from a terrestrial synestia, a giant spinning donut of vaporized rock that formed when planet-sized objects collided. Image by Sarah Stewart/UC Davis based on NASA rendering.
The new, “synestia theory” suggests a Mars-sized object smashed into the proto-Earth. The “giant impact” vaporized about 10 percent of the rock and liquefied the rest, and created a rapidly spinning donut-shaped mass of vaporized rock called “synestia”. The synestia eventually shrunk and cooled. Computer models demonstrated that the Earth subsequently emerged about 1,000 years after the moon.