What is the significance of Chang'e-5 less than 2 billion years old lunar samples?

1.97 billion years ago, lava was still flowing on the Moon's surface, and now there is proof in the form of rocks.

According to a report published in 'Science', an international team of planetary scientists and researchers from China, Australia, Sweden and the United States has arrived at this discovery.In order to reach this conclusion, they studied samples collected by the Chinese National Space Agency during the Chang'e-5 mission.

Chang'e-5 was an unmanned mission consisting of a robotic lander that landed on the near side of the moon (the side facing Earth) in December 2020.

One of the mission goals of Chang'e-5 was to look for evidence of the moon's youngest volcanic eruptions.

1.7 kilograms of lunar rocks were returned to Earth, the first samples from the Moon collected since 1976 with the Soviet Union's Luna 24 mission.

The number of impact craters on the lunar surface has previously been used to predict the age of volcanic rocks on the Moon, but it is impossible to confirm without samples to examine.

At the Shrimp centre in Beijing, China, the samples were analyzed using a sensitive high-resolution ion microprobe instrument. Following analysis,scientists determined that these lava eruptions are 1.97 billion years old, which is a billion years younger than previously dated lava from the Moon.

This has presented a new scientific mystery.

Volcanic eruptions are caused by molten material generated by heat inside a planet.For a moon-sized planet, the heat would have been dissipated long before these eruptions 2 billion years ago.

The question that arises is how a small planetary body like the Moon, which was formed 4.5 billion years ago, could have retained enough interior heat to continue producing volcanic eruptions 2.5 billion years after it was formed.

During the Moon's geological history, the surface of the Moon experienced many volcanic eruptions that formed large sheets of basaltic rock known as the lunar mare. They appear as dark patches on a lunar surface.

However, most of the volcanic activity took place between 3 billion and 4 billion years ago. Based on the age of rock samples from the Apollo and Luna missions, as well as meteorites originating from the Moon, scientists have confirmed this.

So, what isgoing on?Scientists have a few theories

Although scientists have previously proposed that the high concentration of radioactive elements found inside the lunar interior may have contributed to the melting of rocky stone, the composition of these samples indicates this was not the cause of the melt.

Tidal heating could also have played a role, in which heat is generated in the Moon's interior due to the stretching and squeezing caused by the gravitational interaction between the Moon, Sun and Earth.

Another possibility is that the composition of the mantle of the Moon contributed to a lower melting temperature, explaining how molten material formed.