- Jonathan Amos
- BBC Science Correspondent
The rock samples brought back from the moon by China’s “Chang’e 5” in December last year were very young.
Of course these are relative, but analysis shows that the basalt material, the solidified residue of the lava flow, is only 2 billion years old.
Comparing it with the samples brought back by Apollo astronauts, they all have a history of more than 3 billion years.
China’s “Chang’e-5” was sent to a location on the moon called “Oceanus Procellarum” (Oceanus Procellarum). This was carefully selected. In order to increase the knowledge gained from previous sample sampling, the last sample was collected by a Soviet detector in 1976.
Xiaochao Che of the Beijing Ion Probe Center and his colleagues led the chronological analysis of the Chang’e-5 samples, but they worked with an extensive international alliance.
The chronological data they derived is interesting because one might expect such a small celestial body to have cooled and ceased activity for a long time, which proves that volcanic activity on the moon is still going on.
Theorists will now seriously think about what heat source might sustain the later activities.
It does not appear to be driven by concentrated radioactive decay, because the Chang’e-5 sample does not contain a large number of chemical elements related to this effect.
“Another possibility we discussed in the paper is that maybe the moon can stay active longer because it interacts with the Earth’s orbit.” Co-author Katherine Joy (Katherine Joy) speculates at the University of Manchester in the United Kingdom.
“Maybe the moon swings back and forth in its orbit, triggering what we call tidal heat. So, a bit like the moon triggering tides on the earth, maybe the earth’s gravitational effect can stretch and bend the moon, causing frictional melting,” she told the BBC.
A very important result of this research is that it helps calibrate the crater counting technique, which is used to date the planet’s surface.
Scientists believe that the more craters they see on a surface, the older the terrain is; and, in reverse, it is also obvious: few craters indicate that the surface has been recently paved or reshaped.
But this technology must be based on some absolute dates derived from measured samples. For the moon, the chronology is not limited to 1 billion to 3 billion years ago.
Today, the Chang’e-5 sample provides a precise coordinate point in the middle of this time.
Professor Brad Jolliff from Washington University in St. Louis is another co-author of the consortium. He now hopes that China’s next sample return mission will be to an area on the far side of the moon called the Aitken Basin in Antarctica.
This large crater, about 2500 kilometers wide and 8 kilometers deep, was created by a stunning impactor in the early lunar history.
“If the’Chang’e 6’reaches Aitken, Antarctica, it will provide us with the age of the oldest large impact basin on the moon, which will provide a very different calibration part between 4 and 4.5 billion years ago. We don’t know at that time. What has changed in the large impactor, and samples from the Aiken Basin in Antarctica may answer this question.”
After the launch of Chang’e 5, China’s national space program was shocking in the next few months.
Within 6 months after the lunar rover returned to Earth with a rock sample on December 16, 2020, another spacecraft successfully entered the orbit of Mars and placed a rover on its surface. Moreover, Chinese astronauts have begun to build a new space station for the earth.