The Moon could have formed in a few hours, when material from Earth and another star was put into orbit after the impact. Normand Grondin's report.
Earth's natural satellite could have orbited the planet virtually instantaneously following a giant impact with another celestial body, computer simulations by scientists from NASA and the Institute of Computational Cosmology associated with Durham University in the United Kingdom.
The vast majority of astrophysicists have agreed for a few decades to explain the presence of the Moon in Earth's orbit by a giant impact, which occurred 4.5 billion years ago, between the primitive Earth and a protoplanet called Theia.
Theia hits Earth hard
This object was probably as massive as the planet Mars. For comparison, the asteroid that would much later wipe out the dinosaurs was only the size of Manhattan.
The shock of the fusion of the two stars would have precipitated a large quantity of matter in the orbit of the Earth, which would then have agglomerated over a period of several tens of years, even hundreds of thousands of years, to form the Moon.
The Moon, Earth's natural satellite.
- It has a diameter of 3476 km, which corresponds to a quarter of that of the Earth (12,742 km).
- It is at an average distance of 384 400 km from Earth.
- The temperature there varies between -248°C and +123°C.
- It is the largest moon in the solar system compared to the size of its planet.
The new theory posits a scenario similar to the giant impact, but which would have happened over a much faster period of time, almost instantaneously.
Start of the widget. Pass the widget?End of widget. Back to the top of the widget?
Researcher Vincent Eke and his colleagues have created ultra-detailed, high-resolution simulations of hundreds of collisions at different angles of impact, velocities, planetary rotations, and masses between Earth and Theia.
This work revealed that the low-resolution simulations conducted to date may miss some important aspects of large-scale collisions that had not been possible to imagine in previous studies.
The simulation thus shows that the Moon would then have formed at very high speed, in just a few hours, especially from material coming from the Earth.
This hypothesis fits better with analyzes of rocks brought back from the Moon. The Moon would therefore not be composed of only 30% terrestrial matter, as the classic hypothesis suggests, but of 60%.
The scenario of an instantaneous Moon birth thus helps explain unsolved mysteries, including the Moon's tilted orbit relative to Earth's equator. This scenario also explains why the primitive Moon, which would have preserved the core of the protoplanet, is not completely melted. In addition, its thin crust is said to be composed of material inherited from Earth.
Collisions are an essential part of how planetary bodies form and evolve.
< p class="e-p">Better understanding the appearance of the Moon allows us to better understand the evolution of our own Earth, says Vincent Eke.
The impact with Theia and the fall of meteorites during Earth's evolution certainly explains, in part at least, how the Earth was able to gather the ingredients necessary for the appearance of life.
“The more we can simulate and analyze what is at stake in these collisions, the more prepared we will be to understand how a planet can evolve to become habitable. »
— Vincent Eke
The analysis of samples from deeper areas below the lunar surface that will be brought back to Earth by future NASA Artemis missions will allow in the next few years to confirm – or disprove – the theory of instantaneous planet formation.
Until then, the Moon will continue to slowly recede , at the rate of three centimeters per year, so that in a few million years, it will leave the gravitational grip of the Earth.