This is how the Moon was left with two very different faces

A new study of craters on the surface of the Moon tends to associate the asymmetry between the two lunar faces with the impact of a massive meteorite at the level of its south pole, following the hypothesis that the latter would thus have motivated the volcanic processes at the level on its visible side, facing Earth.

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[EN VIDÉO] GRAIL films the dark side of the Moon
First images taken by the GRAIL lunar probes showing the far side of the Moon. The dark side of the Moon is the one we never see from Earth. ©NASA

The Moon constantly presents the same face to the Earth: it is blocked by the effect of tidal wave (its period of rotation is equal to its Période de révolution de la Terre
En mécanique céleste, on qualifie de « mouvement de révolution » un déplacement circulaire ou elliptique et périodique tel…” data-image=”” data-url=”” data-more=”Lire la suite”>revolution period
), and therefore has a hidden face, invisible from Earth. The differences between the two faces came to light from the first Overview of the far side by the Soviet probe Luna 3, in 1959: scientists then discovered a rough and cratered surface (called the highlands), unlike the near side which is covered with lunar seas – wide plains basalt dark and smooth in appearance.

Would different chemical compositions explain the lunar asymmetry?

But the elements that distinguish the two lunar faces are not only geomorphological: the post-Luna 3 missions also revealed significant differences in the geochemical composition between the two faces. The visible side houses a anomalies of chemical composition called stormy terrain (PKT), characterized by high concentrations of potassium (K), and Liste des terres rares
Il s’agit de :
15 lanthanides (éléments chimiques dont le nombre atomique est compris entre 57 et 71) :le lanthane ;le cérium ;le praséodyme ;le néodyme ;le prométhium ;le samarium…” data-image=”” data-url=”” data-more=”Lire la suite”>strange land
(REE), in Généralités
Symbole : PNuméro atomique : 15Électrons par…” data-image=”” data-url=”” data-more=”Lire la suite”>match
(P) as well as other heat-producing elements such as thorium (Th). This anomaly is widely represented in and around the ocean of Il n’existe pas de caractéristiques précises pour…” data-image=”” data-url=”” data-more=”Lire la suite”>storms (ocean of storms) and is found globally on the visible side, but appears much more sparse on the hidden side.

Scientists currently agree in pointing the finger at the PKT chemical anomaly to explain the dichotomy between the two lunar faces: characterized by high concentrations of heat-producing elements, this anomaly could have had the ability to motivate late volcanic processes at the lunar level. visible. side of our satellite. But the mechanism at the origin of this anomaly was still unknown: also presenting high concentrations of incompatible elements (which tend to concentrate in the phase liquid During the fractional crystallization one’s Formation du magma
Il se forme à haute température et sous haute pression…” data-image=”” data-url=”” data-more=”Lire la suite”>magma
), the elements that characterize the KREEP, therefore, would have crystallized last and, therefore, would have relatively uniformly formed the upper layer of the KREEP. moon coat ; a new study seems to indicate that the impact of the meteorite at the origin of the formation of the South Pole-Aitken Basin (second largest impact basin in the Solar systemlocated at the lunar south pole, and of which a small part is represented on the near side – 2,500 kilometers in diameter by 12 kilometers deep) could have redistributed the elements that make up the KREEP preferentially at the level of the near side : indeed, the formation of the South Pole-Aitken basin seems to correspond in time to the formation of the last lunar maria.

A colossal meteorite impact would have redistributed chemical elements around the Moon

The team of researchers then produced La modélisation numérique
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to simulate the effect of Vague et houle
Notons que, au large, on parlera plus volontiers de…” data-image=”” data-url=”” data-more=”Lire la suite”>vague
of the heat generated by such an impact in the interior of the Moon, and in a possible redistribution of KREEP elements. His simulations proved to be largely conclusive: for any simulated impact scenario (from a direct and violent impact to a low impact La vitesse ayant une direction et une intensité est représentée par un vecteur, le vecteur vitesse. La vitesse relative est la vitesse d’un corps par rapport à un autre ou par rapport à un repère.” data-image=”” data-url=”” data-more=”Lire la définition”>vitesse and low angle), the amount of mobilized KREEP elements varies, but consistently results in high concentrations of these elements around the opposite side, consistent with the observed KPT anomalies. Thus, scientists support the idea that the impact of the meteorite at the origin of the South Pole-Aitken basin would have made it possible to excavate Matière organique, matière azotée, etc.
Il existe différentes familles comme :

la matière organique, qui constitue les êtres vivants (animaux ou végétaux) ou…” data-image=”” data-url=”” data-more=”Lire la suite”>matter in it Le manteau, pourtant solide, est animé de courants de convection qui…” data-image=”” data-url=”” data-more=”Lire la suite”>Coat up and down la croûte continentale forme, comme son nom l’indique, les continents. Elle est essentiellement de nature…” data-image=”” data-url=”” data-more=”Lire la suite”>Cortex.

And the dating arguments of different lunar structures on the visible side seem to support this idea: the crater count in the PKT zone indicates that this formation would be later than the formation of the impact basin of the south pole, and the oldest basaltic seas . it would be dated at -4.3 billion years (about 200 million years after the Aitken impact); in fact, their model shows a thermal asymmetry between the two faces for more than 600 million years after the impact, caused by the asymmetry in the chemical composition and the motivating volcanic processes on the near side.

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