The Chinese brought with them the moon's youngest stones

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Published 12 October 2021 at 08.10

Abroad. The Chinese lunar landing in 2020 brought with it rocks that were a billion years younger than previous samples – which shows that volcanism lasted a very long time before the moon became cold and hard.

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During the Chinese, unmanned lunar landing Chang’e-5 in December 2020, a soil sample was dug up and transported back to Earth. This has not happened since 1976.

The Swedish Museum of Natural History is part of the exclusive group of researchers who participated in the analysis of the rare soil sample and the results are published in the journal Science.

In the soil sample, the rock basalt was found. It was dated with a method developed at the Swedish Museum of Natural History and is based on measuring the presence of lead isotopes that have a known rate of degradation.

The results show that the soil sample contains basalt which is “only” 2 billion years old. Earlier lunar samples from the Apollo expeditions in the 1970s have been dated to 3 billion years or older.

The ion micro probe found in the Nordsim lab at the Swedish Museum of Natural History has been used several times to date samples from the Apollo and Luna expeditions. This time the dating was done with similar instruments in China.

Basalt can form in magma at temperatures above 1000 degrees. Volcanoes where magma has been thrown up on the surface and solidified is really the only reasonable explanation for how basalt may have formed on the moon.

Basalt is exactly what comes out of the volcano at La Palma right now.

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Other temperature rises on the moon occur during large impacts of meteorites and asteroids that form the craters of the moon, but from this area there is no evidence of such large impacts as would have been required for the mantle to melt and cause flows of basalt.

If volcanoes and a heated interior existed on the moon as long as 2 billion years ago, it affects our knowledge of the formation of the solar system and its chronology. On all planets and moons where there are craters, these are used as timestamps to map relative times in the evolution of the solar system. The dating of the moon's rocks is one way to calibrate this mapping and is therefore important.