The moon may have hosted an ocean of magma for 200 million years according to new findings- considerably longer than previously thought.
So far, the leading explanation for how the moon came to be is that it came as the result of a collision between two protoplanets or young planets. One of those was the nascent Earth, and the other: an object the size of Mars known as Theia.
"An important outcome of this scenario is that the early moon, which accreted from the debris of this giant impact, was very hot — hot enough for its rocky mantle to be largely molten and form what we call a magma ocean," says lead author of the new study, Maxime Maurice, a planetary scientist at the German Aerospace Center in Berlin.
Although the idea of the moon being home to a large magma ocean is generally accepted, how long it took to solidify remains a mystery. While previous models suggest that this happened quickly- just some tens of millions of years- current findings indicate otherwise.
In the new study, researchers built a model to consider many processes disregarded until now to calculate how quickly the lunar magma solidified. One such process is mantle convection- the way molten rock churns to the surface of a planet, much like how volcanoes work on Earth.
In accounting for these features, they found that the luna magma sea may have taken between 150 and 200 million years to solidify, or ten times longer than previously thought. The model also suggests that the moon is between 4.4 billion and 4.45 billion years old- around 50 million to 100 million years younger than previously suggested.
Should these findings be correct, it means that large-scale collisions, such as those that birthed the moon, were still happening 150 million years after the solar system came to be.
"It was very exciting to see that our findings had these kinds of broad implications," says Maurice.