The moon was formed in a matter of hours

A supercomputer simulation at NASA’s Ames Research Centre points to this theory.

The NASA and Durham University simulation on the moon’s origin. | Photo Credit: NASA’s Ames Research Center

Billions of years ago, the earth was hit by an object the size of Mars, called Theia—and out of that collision the moon was formed. How exactly that formation occurred is a scientific puzzle researchers have studied for decades.

Most theories claim the moon formed out of the debris of this collision, coalescing in orbit over months or years. A new supercomputer simulation puts forth the theory that the moon may have formed immediately, in a matter of hours, when material from the earth and Theia was launched directly into orbit after the impact. The results of the simulation done at NASA’s Ames Research Centre were published in a recent issue of The Astrophysical Journal Letters.

The simulations used in this research are some of the most detailed of their kind, operating at the highest resolution of any simulation run to study the moon’s origins or other giant impacts, said a NASA release.

Earlier theories could explain some aspects of the moon’s properties quite well, such as its mass and orbit, but with major caveats. One outstanding mystery has been why the composition of the moon is so similar to the earth’s, as seen from isotopic signatures of lunar samples.

In this theory, more earth material is used to create the moon, particularly its outer layers, which helps explain this similarity in composition.

There have been other theories proposed to explain these similarities in composition, such as the synestia model (where the moon is formed inside a swirl of vapourised rock from the collision) but these arguably struggle to explain the moon’s current orbit.

This faster, single-stage formation theory could also lead to answers for other unsolved mysteries,potentially explaining properties like the moon’s tilted orbit and thin crust.

As scientists gain access to samples from other parts of the moon and from deeper beneath the moon’s surface, simulated scenarios will be able to indicate how the moon has evolved over billions of years.

“The more we learn about how the moon came to be, the more we discover about the evolution of our own earth,” said Vincent Eke, a researcher at Durham University and a co-author on the paper.