Chinese spacecraft that is changing our perception of the moon

change 5 samples revea

China is a participant in the new space race. The last decade has shown its technological and industrial power to carry out a series of missions to learn more about our satellite and pave the way for future manned missions. The most recent of these, Chang'e 5, and the samples it brought back to Earth allowed researchers to offer a better perspective on the history of the Moon.

Change 5
Graphical representation of the Chang'e 5 probe during sample collection. These provided evidence of a large volcanic eruption two billion years ago and a constant shower of micrometeorites.

Chang'e: the goddess of the Moon

The Chinese Chang'e probes, named after the goddess who inhabits the Moon in Chinese mythology, are part of the program that seeks to better understand our satellite and to test the technologies needed to visit it with crews. For this reason, each mission has been more complex than the previous one, the most recent being Chang'e 5. For the first time since 1976, samples of the lunar regolith were brought to Earth, allowing researchers to study them with new technology developed in recent decades.

Chang'e 5 successfully landed on December 1, 2020 near Mons Rümker, an ancient volcano in the Storm Ocean. Employing a robotic arm collected a total of 1 731 grams of moon regolith from the surface and to a depth of 1 meter using a drill.

1216px Landepunkt Change 5
Orbital image of the Mons Rümken region in the Storm Ocean. The Chang'e 5 landing site is demarcated with a black circle in the lower left.

Rediscovering the lunar soil

While the Apollo and Luna missions explored equatorial zones on the visible side of the Moon, Chang'e 5 reached a higher latitude of 43 degrees north, an area far removed from those previously explored. This is to get a better perspective of the Moon's history, as well as its previous volcanic activity and meteorite impacts. The age of the site is estimated at about 1.9 billion years, as well as a considerable presence of titanium oxide.

One of the most valuable parts of sample analysis, compared to information collected by orbiters, is the ability to study the material on a smaller scale. For example, the size distribution of particles provides information about their physical properties. The regolith collected shows an average grain size, concentrated in the 50 micrometers, similar to that found by Apollo and Luna. Likewise, the relative uniformity and filtering confirms the estimated age.

Change 5 regolith
Microscope images of cross sections of different basalt samples found in the material recovered by Chang'e 5.

A major concern was the possible contamination of the regolith by gases expelled by the downdraft motor. Since these can alter the grain size distribution and cause false positives in the measured maturity of the material.

The clasts, or deposits, show a great variety of glasses on their surface. They are divided into two classifications. The first has round shapes and dark or greenish tones. While the other is irregular and full of fractures. Where both types are joined together as a weld by the great heat released in the impacts of micrometeorites. In addition, the small variation in isotopes in various layers is evidence that crystallization occurred at different stages of cooling of the same lava flow.

Laying the foundation for the future

One of the biggest revelations was the water content, which, when extrapolated, evidences the possible existence of large deposits of this precious liquid that can be extracted and exploited.

Future probes such as China's Chang'e 6 and the U.S. Artemis missions are expected to provide more samples to contribute to the understanding of the Moon. They offer us the possibility of rediscovering the history of our own planet, and give us key clues to take care of it.

Reference: Chen Y., Hu S., Li J., (2023). Chang'e-5 lunar samples shed new light on the Moon. The Innovation Geoscience

Francisco Andrés Forero Daza