The moon is a big part – not a lumpy ball of grains

British astronomers have a new theory about the origin of the moon. According to the new theory, the moon did not form from accumulated debris left by a violent collision between the Earth and a smaller planet, which is the common idea of ​​moon formation. On the contrary, the Moon as a whole could have broken off in one fell swoop and entered into orbit around the Earth as a result of this same collision.

To reach this conclusion, astronomers simulated the formation of the moon about 4.5 billion years ago on a supercomputer in more detail than was previously possible. they posted their results in Astrophysical Journal Letters.

The composition of the moon according to the new theory is more consistent with measurements of moon rock formation than the formation of the moon in the traditional way.

But Wim van Westrenen, a lunar researcher at the Free University of Amsterdam who was not involved in the study, has reservations about the new theory. “Although the chemical composition is more similar now, the distribution of those elements in the moon is probably incorrect here. According to the new simulations, the composition of the inner part of the moon should be very different from the outer composition. This is not what we observe in the moon samples. We see That the young moon was very hot and therefore must have mixed well.”

lying around the earth

The moon was formed about 4.5 billion years ago when the young Earth collided with Theia. This is a hypothetical planet smaller the size of Mars. According to the current idea, the granules would have been thrown around the Earth like a disk. This could have come together at a later time. Within a few thousand years, the moon formed.

Computer simulations show that if the Moon had really formed in this way, the Moon would have been made up of more than half of Theia matter. But from samples of the moon that astronauts brought back from the Apollo missions to Earth, it appears that the moon is made up of 99 percent of Earth-derived materials.

English astronomers simulated the collision between Theia and Earth at a higher resolution than previous models and came up with a new theory that better fits the observed structure. According to the new theory, there was also a collision between Theia and Earth 4.5 billion years ago. But instead of creating the granules first, the moon shot up on impact and kicked into its orbit within hours. According to simulations, such a moon is made up of 60 percent of the matter of the Earth.

Van Westrenen: “This is a lot more ground material than in the older simulations, which matches up better with the observations – but it’s not the 99 percent we need. Here, too, additional tricks are needed at the end to explain the difference between simulations and observations, Just as with the old theory. However, it is interesting that through detailed simulations of the history of the Moon, we see different things from the old models. That is it.”