The planets of our Solar System, including the Earth, were formed by collisions and gradual accretions of rocky bodies called “protoplanets”. However, the processes involved in these gigantic collisions are still poorly understood and the various models proposed often lead to a paradox: the debris observed in the asteroid belt is not sufficient to describe the formation of all the planets of the Solar System. . However, new results suggest an explanation that would solve this problem.
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[EN VIDÉO] These are all known asteroids in our Solar System Look how many there are: here are all the asteroids identified by astronomers since the first discovered in 1801. The number of discoveries has literally jumped since the end of the 20th century.
During the formation of the Solar System, the terrestrial planets (Mercure, Venus, Earth and Mars) are believed to have been formed by collisions and accretions between smaller rocky bodies, until a embryo planetary.
Solid debris is missing to explain the formation of the Solar System
These violent collisions are supposed to have generated a lot of debris, which would then have escaped the attraction of the planetary body in formation and would have been put in orbit around Soleil, forming an asteroid disk. This disc of debris, we still observe today in the form of the asteroid belt main, which lies between the orbits of Mars and Jupiter. In principle, the astrophysicists should find in this asteroid belt the markers of the formation of the Solar System. But this is not the case.
The amount of solid debris orbiting beyond Mars is not sufficient to explain the formation of the entire Solar System. Some models explain this shortcoming by the fact that part of the asteroids in the debris belt would have subsequently bombarded the planets in formation. But even in this case, the mineralogical composition of the elements of the asteroid belt does not correspond to what is expected. In particular, it lacks meteorites rich in olivine, who is the mineral main component coat from terrestrial planets. A paradox known as ” Missing mantle problem Which has remained unexplained for decades.
Rocks vaporized under the power of impacts
Two researchers from Arizona State University (USA) attempted to solve this problem. They thus simulated and modeled collisions of protoplanets to study the processes thermodynamics intervening during these events. Their results, published in the journal The Astrophysical Journal Letters, show that these large collisions ultimately generate little solid debris, but rather gas. Indeed, under the power of the impact, some of the rocks are literally vaporized! While the solid debris will agglomerate in residual discs like the asteroid belt, the gases resulting from the vaporization will more easily escape from the Solar System, thus leaving no trace of the collusive events that created them.
These results provide a solution to the problem of the lack of solid debris present in the asteroid belt and to the paradox of ” Missing mantle problem ».
This proposal could also make it possible to understand the moon formation. The terrestrial satellite would thus have as its origin the solid debris resulting from the formation of the Earth. In previous models, the Moon would then have been heavily bombarded by debris orbiting the Sun, greatly compromising or greatly influencing its formation. However, this is not what seems to have happened. In the hypothesis developed by Gabriel Travis and Harrison Allen-Sutter, who propose that a significant part of the residual material is in fact in the form of gas, the meteoritic impacts on the Moon are much less important and do not compromise its formation.
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