Photo d'illustration. La Lune.

What if the Moon had formed in just a few hours? That’s what a new simulation suggests.

Our Moon has always been part of the decor, so to speak. And yet, it still remains very mysterious. His training, in particular, is still debated. The most popular theory is that it resulted from the giant impact between Earth and an embryo Mars-sized planet, Theia, but how long did it take to form the satellite? A new simulation offers a slightly different answer.

What if the Moon had formed in just a few hours?

The results of the research published in The Astrophysical Journal Letters suggest that materials sent into orbit after the impact could have come together almost immediately, in just a few hours, to form the Moon. “This opens up a whole new range of possible starting points for the evolution of the Moon,” says Jacob Kegerreis, postdoctoral researcher at theAmes Research Center of NASA and lead author.

The previous hypotheses justified certain properties of the Moon, including its mass and its orbit, but did not explain the chemical compositions close to those of the Earth. The idea that Theia was pulverized and then mixed with terrestrial matter does not lead to the conclusion of such a similarity between the two isotopic signatures. Unless, of course, Theia was very Earth-like.

This is suggested by a new simulation

With this new high-resolution digital simulation carried out on a supercomputer, a larger part of the Earth’s mantle would have been involved in the creation of the Moon, which would explain the resemblance in the composition. The model suggests that the Moon would be composed of 60% material from the Earth against 30% for the initial theory. And if our satellite had indeed formed quickly after the collision, this would have had an impact on its cooling, a lesser quantity of rock would have been “melted” during its formation, to lead to the composition that we know today .

In addition, this theory would provide insight into some poorly understood properties of the Moon, such as its inclined orbit or its relatively thin crust. There is no doubt that the lunar samples recovered below the surface and brought back by the Artemis missions should help researchers confirm or invalidate this hypothesis.

And as usual, these discoveries could give us a better understanding of our own planet. Vincent Eke, researcher at Durham University and co-author of the article, said that “the more we learn about the birth of the Moon, the more we discover the evolution of our own Earth. Their histories are intertwined and could find echoes in histories of other planets altered by similar or very different collisions.”

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