Chang’e-5 return capsule holding lunar specimens.
Credit: National Astronomical Observatories, CAS


The first batch of lunar samples retrieved by China’s Chang’e-5 mission were distributed on Monday to domestic scientific research institutions.

The samples were picked up from the Moon in December 2020 by the Chang’e-5 lunar probe, the first lunar soil sample collection brought back to Earth in more than four decades. The probe returned with 1,731 grams of lunar soil.

More than 17 grams worth of lunar samples brought back by the Chang’e-5 probe were distributed to 13 institutions, including the Chinese Academy of Sciences, China University of Geosciences (Beijing), China University of Geosciences (Wuhan), and the Sun Yat-sen University.

Credit: CCTV/Inside Outer Space screengrab

Under the microscope

The lunar soil seen by the naked eye is like dry black sand, but with finer grains. But under the microscope, it is a whole different view.

“This is the lunar soil, the original sample under the microscope that has not been crushed or polished. We can see many rock pieces in the view, which should be part of basalt. After its disintegration, some pieces still retain their original mineral composition, which we call debris. They are just physically smaller but their structure and mineral composition remain the same as the basalt. For other rock pieces, they actually turned into monominerals, that different types of minerals are separated. You can see the yellow ones in the view are generally olivine, brown ones are usually glass, white are normally plagioclase, and some dark ones are generally pyroxene. These are the main mineral components in basalt,” said Li Chunlai, deputy chief designer of the third phase of lunar exploration project, also chief engineer of the ground application system.

Chinese President Xi Jinping inspects Chang’e-5 lunar sample return capsule.
Credit: CCTV/Inside Outer Space screengrab

Physical fragmentation

Li told China Central Television (CCTV), unlike the soil on the Earth’s surface, the particles of the lunar soil are relatively small due to the influence of many factors.

“The environment on the Moon’s surface is very harsh. The temperature could reach about 160 degrees Celsius when the sun is shining and drop to minus 180 degrees Celsius when there is no sunlight. With a temperature difference of about 340 degrees Celsius, the rocks constantly undergo thermal expansion and contraction which result in disintegration. This is one factor. Another factor is that the Moon’s surface could be hit by many celestial bodies. The impact could cause physical fragmentation of the rocks,” Li said.

And since the Moon has no magnetic field at present, the solar wind can directly bombard the rocks on the Moon’s surface, which gradually result in the breakdown or even powdering of the rocks.

“The particles could measure a few tenths of a micrometer, a few millimeters or even centimeters. But on average, they are less than 10 microns, which is very, very broken. This is inconsistent with our original cognition and also different from the Apollo sample. It is a very fine lunar soil sample,” said Li.

Credit: CASC

Ensure safety of samples

Liu Jizhong, director of the Lunar Exploration and Space Program Center under the China National Space Agency (CNSA) told CCTV: “Our lunar sample management rules have clear provisions that part of the samples will be used for scientific research and part will be used for public good. After the preliminary study is completed and the re-study would yield little results. We then display them for the public good, letting more people to know more about the Moon.”

Credit: CCTV/Inside Outer Space screengrab

In order to ensure the safety of the lunar samples, the CNSA is planning to store up some lunar samples in Shaoshan, central China’s Hunan Province, in preparedness against disasters.

“We plan to distribute the samples as much as possible for scientific studies. We must also retain some for future sustained studies. We have a base for ex situ conservation of some samples. All these serve as the basic for following up studies,” said Liu.

Go to these China Central Television (CCTV) videos that focus on the lunar samples at:

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