by China achieved a historic feat by returning the first-ever sample from the lunar side in June 2024. The lunar lander, Chang’e 6, used a robotic scoop and drill to retrieve approximately 5 pounds (2 kilograms) of collect rocks and soil. . These samples returned to Earth on June 25, 2024.
Chang’e 6 achieved the feat of two previous Chinese missions: Chang’e 4, which landed softly on the far side of the Moon and used a rover to explore the surface, and Chang’e 5, which sampled back from the side of the moon.
Scientists hope that the Chang’e 6 samples will not only provide important geological information about the Moon but also improve their understanding of Earth and the early history of the solar system.
Lunar scientists like myself have been interested in the far side of the Moon since the Soviet Union’s Luna 3 mission in 1959, which showed that the far side of the Moon looks very different from its near side.
The far side of the Moon
Because the same side of the Moon always faces the Earth, you can only see the far side with spacecraft. The far side is not permanently dark – it alternates between two weeks of daylight and two weeks of night, just like anywhere on the Moon.
Images taken by spacecraft show that about a third of the surface near the Moon is made up of smooth dark plains, and that these plains are only about 1% of the far side.
These dark plains were once volcanic lava flows, similar to those found on Earth in Hawaii, eastern Washington and India.
Images taken from lunar orbit tell researchers that these plains once contained volcanic vents, cones, domes, pitfalls and channels.
Only the Chang’e 4 and Chang’e 6 missions landed on the far side of the moon, while 25 spacecraft made soft landings on the far side. A side landing mission is more difficult because mission control cannot see or speak directly to the spacecraft. So a second spacecraft is needed to pass information between the lander and Earth. China used its Queqiao-2 orbital satellite, launched in March 2024.
Chang’e Gambling 6
On June 6, 2024, Chang’e 6 landed within the giant South Pole-Aitken basin, which is about 1,550 miles (2,500 km) wide and 5 miles (8 km) deep. It is the solar system’s largest impact structure: a bowl-shaped feature created when an asteroid collides with a body, causing a massive explosion.
Superimposed on top of the South Pole-Aitkin is a slightly younger and much smaller impact structure called the Apollo basin, about 308 miles (492 km) in diameter.
A drilling core reveals impact basins in the Moon’s deep interior. For example, the impact that created the South Pole-Aitkin basin may have removed some of the lunar crust, exposing materials deep within the Moon – up to 62 miles (100 km) down. Apollo’s later influence would make him even more content. Therefore, it is likely that the returned samples will contain some rocks that are different from those in the current sample collection.
Chang’e 6 landed here on some of the rare volcanic deposits, long ago. Analyzing the composition of the volcanic rocks brought back by Chang’e 6 might help researchers find out why there are so many more volcanic deposits on the other side. Scientists will also be able to compare the ages of rocks on the far side with rocks from volcanic eruptions on the near side that occurred about 3.9 to 3.2 billion years ago.
It will help scientists refine other methods, such as crater counting, used to estimate the age of surface formations on planets.
Since planetary surfaces accumulate more craters the longer they are around, researchers can estimate the age of a planetary surface by comparing the number of craters they can count to those generated by a simulation model. But crater counts aren’t very accurate—actual rock samples can help researchers learn how to improve these methods.
Revealing secrets from the time of the Moon’s meltdown
Researchers theorize that the Moon, along with several rocky planets, was almost entirely molten. So, for a short period of time early in its history, the Moon was nothing but lava with little or no solid rock.
The Chang’e 6 landing site could contain materials from the Moon’s mantle – the layer beneath its crust. These samples could help scientists understand how the Moon changed from an ocean of magma to having geological layers – a crust, a mantle and a solid core.
Data from these samples may also provide clues about Earth’s evolution in the final stages of planetary formation. Scientists predicted that about 4 billion years ago, many asteroids and comets rained down on rocky planets like Earth. This period is known as the “lunar cataclysm” period. Studying certain rocks from crater impacts on the Moon could help scientists learn more about this era.
Since the South Pole-Aitkin basin is the oldest well-preserved structure on the Moon, it may contain evidence of whether the number of basin-forming impacts occurred over a longer period of time, such as 500 million years , or a shorter period, for example. 200 million years. Knowing the timescale would help gauge the intensity of the impact during the formation of the solar system.
A scientific gift from beyond
Extraterrestrial objects – such as the Moon, Mars, asteroids and comets – are gifts that keep on giving.
Scientists will preserve these samples and store them in laboratories to keep them the same. This process will distribute some of the valuable samples for analysis with state-of-the-art equipment. The rest will be stored for future generations of scientists to investigate new questions that arise decades or thirty years from now.
Science makes the most progress when scientists share ideas, data and examples. At the end of 2023, the China National Space Administration provided the samples from Chang’e 5 to a series of international researchers. I expect to see a similar sample sharing program for Chang’e 6 samples.
This division, however, does not go both ways. NASA cannot share the samples they are keeping directly with Chinese researchers because of the Wolf Amendment, which prohibits NASA from using funds to collaborate with China on any program.
China’s future lunar exploration plans include the Chang’e 7 and 8 missions, planned for 2026 and 2028, respectively. These missions will land at the south pole to search for water ice, carbon dioxide ice – also known as dry ice – and methane in the form of ice. NASA’s recently canceled VIPER rover had similar goals. These missions will help China determine where to place its International Lunar Research Station, planned for 2030.
This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. Written by: Jeffrey Gillis-Davis, Arts and Sciences at Washington University in St. Louis
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Jeffrey Gillis-Davis does not work for, consult with, own shares in, or receive funding from any company or organization that would benefit from this article this article, and did not disclose any relevant connections beyond their academic appointment.
