The Chinese Mission Chang’e-6 has returned to Earth with over 1.9 kg of samples with a hidden face of the moon: this is what this “scientific treasure” tells.
The Chinese Mission Chang’e-6 returned to Earth in June 2024 with over 1.9 kg of samples from the hidden face of the moon. Thanks to this scientific treasure, the Guangzhou Institute of Geochemistry (CAS) group has established the age of the Apollo basin, where Chang’e-6 landed: about 4.16 billion years ago, anticipating the beginning of the so-called Late Heavy Bombardment (LHB) of at least 100 million years compared to previous estimates.
The Late Heavy Bombardment was a period in which the Earth, the Moon and the other rocky planets of the Solar System were affected by an exceptionally high number of asteroids and comets. It seems that it has lasted about 100 million years.
Without sudden peaks. The new study published on Nature Astronomy It reveals that the impact flow during the LHB was not a sudden tsunami between 3.8 and 4 billion years ago, but a slow influx of material over time, dismantling the hypothesis of a sudden peak.
Previously, another study had already dated the gigantic South Pole – Aitken (Spa) Basin – inside which the Apollo basin is located – at about 4.25 billion years ago, based on the Champs of Chang’e -6 and published on National Science Review.
A magma ocean. This discovery follows various other discoveries to bring from the moon champions of the Chinese probe. Among these, a surprising result comes from a study published on Science: thanks to isotopic analysis of the champions, it is confirmed that the moon, in its very first moments, was covered entirely by an magma ocean.
This suggests that the model of the “Crustal Flotation” and the formation of the lunar crust, so far based only on the champions of the nearby side, is also valid for the hidden side.
Volcani at the poles. Another discovery of great interest comes from the basalts collected: some of these have an age of about 2.8 billion years, a sign that the hidden face of the moon has known volcanic activity much more recent than what was thought.
Others, on the other hand, are 4.2 billion years older and thus tell a long and complex fusion and cooling story.
Stratified land. But that’s not all, because a geological study of the landing area then published on Journal of Geophysical Research: Planetsreveals a fluid story: the mission has collected materials linked to three distinct phases of volcanism (EMSAP1, EMSAP2, and EMSAP3), separated from intervals of about one billion years. The unit on which Chang’e-6 (EMSAP2) landed dates back to 2.81 ga, while 30 % of the regolite comes from external craters, transported to the place by impact material of large asteroids.
The face hidden. For decades, we have had clues to the history of the moon only from material from the face addressed to us and this thanks to the samples brought to the ground by the Apollo mission and the Russian missions called “Luna”.
Now, thanks to Chang’e-6, we finally know that there were oceans of magma everywhere, that the hidden face has had active volcanoes up to much more recent periods and that the isotopic and geochimic structure differs-industry parallel but different evolutions in the two hemispheres.