Shulou(Shulou.com)11/24 Report--

CTOnews.com reported on October 22 that since the Chang'e-5 return vehicle successfully returned 1731 grams of lunar soil samples to the ground in December 2020, a total of four batches of 50 grams of lunar soil samples have been distributed to more than 100 scientific research teams, covering the history of lunar geological evolution and the analysis of lunar resources. On October 22, Scientific Progress published the latest research results of Chang'e-5 lunar soil samples online.

According to the Science and Technology Daily, the moon was formed about 4.5 billion years ago and its mass is only about 1% of that of Earth. For such a small celestial body, in theory, it should cool quickly and stop volcanic activity early and become a dead planet. However, last October, Chinese scientists studied Chang'e-5 basalt and found that lunar volcanic activity lasted until 2 billion years ago. Why did lunar volcanic activity last so long?

CTOnews.com learned that in order to solve this problem, Chen Yi's research team selected 27 representative Chang'e-5 basalt cuttings and used the newly developed scanning electron microscope energy spectrum fixed surface scanning technique to analyze the main composition of the whole rock cuttings. Combined with a series of petrological and thermodynamic simulation calculations, the initial magmatic composition of Chang'e-5 basalt was successfully restored. Compared with the initial magma of Apollo low titanium basalt, their origin depth and temperature are inferred.

It is found that compared with the ancient Apollo low-titanium basalt, the initial magma of the young Chang'e-5 basalt contains more calcium and titanium, indicating that there are more calcium-rich and titanium-rich materials in the mantle source of the Chang'e-5 basalt. That is, the mantle of the moon contained more calcium and titanium 2 billion years ago than it did more than 3 billion years ago. At the same time, further simulation results show that the formation temperature of Chang'e-5 basalt is lower than that of Apollo basalt, that is, after more than a billion years of continuous cooling, the temperature of the moon has only dropped by about 80 degrees Celsius.

Based on this, Chen Yi's team proposed a new model of lunar thermal evolution: although the interior of the moon continues to cool slowly, fusible components of late oceanic crystallization of lunar magma continue to be added to the deep mantle, which not only "replenishes calcium and titanium" for the mantle, but also reduces the melting point of the mantle. The mixing process of mantle material in January may be gradually strengthened in the long-term evolution history of the moon, effectively reducing the melting point of lunar mantle rocks, thus overcoming the slow cooling in the interior of the moon and causing long-term persistent lunar volcanism.

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