Simulations suggest the Moon could have formed in five hours
New computer simulations suggest that the Moon could have formed just five hours after the early Earth collided with the Mars-sized protoplanet Theia. This result is possible in the most extreme of the simulated scenarios, when both celestial bodies had the highest temperatures, Live Science reports.
Collision between Earth and Theia
According to the giant-impact hypothesis, the Moon formed about 4.5 billion years ago from debris after Theia struck the early Earth. Samples of lunar rocks delivered by NASA’s Apollo missions support this hypothesis and indicate that the collision occurred approximately 100 million years after the Sun formed.
After the impact, both bodies likely turned into rotating masses of molten rock, which later merged and cooled to form the Earth and Moon as they are known today. The exact mechanism and duration of the formation of Earth’s satellite have remained difficult to determine using models.
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Temperature and material strength
In a study published on September 1 in The Astrophysical Journal Letters, scientists simulated the collision while taking into account different geological properties of Earth and Theia before the impact. Earlier models primarily focused on the masses of the bodies, while the new work considered material strength, including the hardness of their outer layers.
The study’s first author, geologist and planetary scientist Adine Denton of the Southwest Research Institute in Boulder, noted that this characteristic significantly affects the formation of the Moon. Temperature is a key factor in strength: the hot surfaces of the young Earth and Theia could have been soft or molten, which softened the impact, allowed the debris to remain largely intact, and accelerated the Moon’s formation.
Under a scenario in which the bodies were colder and more brittle, the collision would have created a larger field of rocky debris that would have taken longer to merge. The researchers emphasize that the five-hour scenario is only one of the possible ones, as the exact temperature and strength of Earth and Theia at the time of the collision are unknown.
