What are the expectations for lunar sample research?
2024-07-25
The moon, the closest celestial body to Earth, is the place that humans must cross to reach the vast ocean of stars. On June 25, 2024, the Chang'e-6 spacecraft carrying lunar samples from the far side of the moon safely landed in the designated area of Siziwang Banner, Inner Mongolia, marking the successful completion of the Chang'e-6 lunar exploration mission. 1935.3 grams, this is the first human sample from the far side of the moon! Previously, humans conducted 10 sample collections on the moon, but all of them were on the near side of the moon. This is also the second lunar sample collected by our country. In December 2020, Chang'e-5 brought back about 1731 grams of lunar frontal samples, and researchers conducted multiple studies on the samples. What secrets can lunar samples reveal for us? Expected. What is the difference in lunar back sampling? Before the Chang'e-6 mission, humans conducted a total of 10 lunar samples: 3 from the Soviet Union, 6 from the United States, and 1 from China's Chang'e-5 mission, all of which were on the front side of the moon. Chang'e-6 is a backup of Chang'e-5, with the initial goal of sampling from the near side of the moon. But with the successful sampling and return of Chang'e-5 on the near side of the moon, the destination of Chang'e-6 has also changed - the far side of the moon. This is obviously more challenging. On the one hand, humans have less knowledge about the far side of the moon, and lunar sampling faces more unpredictable risks; On the other hand, due to the obstruction of the moon itself, probes located on the far side of the moon are unable to communicate directly with Earth. Therefore, Chang'e-6's landing and sampling on the far side of the moon require the Magpie Bridge 2 relay satellite to provide communication "relay station" services. During the sampling and packaging process of Chang'e-6, researchers will simulate the geographical model of the sampling area based on the probe data transmitted by the Queqiao-2 relay satellite in a ground laboratory 380000 kilometers away from the moon, and simulate sampling to provide support for Chang'e-6's sampling decision-making and various operations. Through this "human-machine collaboration" approach, Chang'e-6 is assisted in timely assessing and controlling drilling risks, and making on-site decisions on subsequent actions. But what if the relay satellite loses contact with the ground? According to Hu Hao, the chief designer of the Chang'e-6 mission, researchers have designed many contingency plans. One of them is to enhance the "autonomous skills" of the Chang'e-6 probe - once there is a problem with the relay satellite, the Chang'e-6 probe can carry out activities autonomously, issue programmed instructions to itself, including drilling, lifting, takeoff, etc., and make autonomous judgments and executions. Of course, this plan was not used in the end, and the relay communication between the Earth and the Moon remained smooth. However, the sampling process still leaves everyone on edge. Like Chang'e-5, Chang'e-6 also has two sampling methods: one is surface sampling, using a robotic arm to carry a sampling device to collect soil on the surface of the moon; The second is to drill and sample, using a drill rod to drill into the lunar surface to a predetermined depth and collect deeper soil layers. Compared to surface drilling, drilling is more difficult and uncertain. After the landing of Chang'e-6, it cannot move its position. If it encounters hard rocks during the drilling process, it is impossible to change the location and drill again. But we cannot give up easily, because drilling is indeed very necessary - from the surface of the moon to the deep, the material composition, particle size and other properties of lunar soil vary greatly, and the scientific information recorded by lunar soil at different depths is also different. In order to ensure "drilling capability", the research and development team of the Fifth Academy of China Aerospace Science and Technology Corporation conducted a large number of ground tests and simulation analyses. They combined the characteristics of lunar soil to design a unique drill bit, and compared multiple design schemes to determine the coring mechanism scheme and corresponding configuration, making it capable of drilling into high hardness rocks. However, researchers ultimately cannot predict all situations. After drilling a little over 1 meter, Chang'e-6 encountered a situation. After unanimous judgment by experts, it is believed that there may be a stone stuck there, "said Hu Hao. This stone is indeed very hard. Should we continue drilling or stop? It's not impossible to keep drilling down. However, "further drilling may result in the loss of some of the achievements made earlier," Hu Hao said. The working time and energy of Chang'e-6 on the moon are limited, and "further drilling may affect the subsequent tasks. This is also the charm of sampling from the far side of the moon and space exploration - unexpected "accidents" always happen in space. After weighing, stop drilling and start sampling. Although it did not reach the expected drilling depth, Chang'e-6 still collected 1935.3 grams of samples from the far side of the moon through the combination of surface sampling and drilling. Our goal is two kilograms of lunar soil, and the container design is so big that it can't fit any more, "said Hu Hao. More than 100 high-quality papers have been published on Chang'e-5 lunar soil research. On June 28, Chang'e-6 lunar samples were transferred from the National Space Administration to the Chinese Academy of Sciences to carry out the storage and processing of lunar samples and start scientific research. Meanwhile, researchers are still conducting research on lunar samples from Chang'e-5. Over the past three years, the National Space Administration has distributed research samples to 131 research teams in China. Through the study of these samples, researchers have achieved significant results in multiple fields such as lunar formation and evolution, space weathering, and resource utilization. Among them, two research results have attracted much attention. One concerns the lifespan of the moon, and the other concerns the water resources on the moon. Similar to Earth, volcanoes and earthquakes are the most intuitive geological phenomena on the Moon. Once the magma activity on the moon stops, it means the geological "death" of the moon. Therefore, when did lunar magma cease has always been one of the major scientific questions in the study of lunar evolutionary history. Previously, research on Apollo lunar samples in the United States showed that volcanic rocks on the moon were over 3 billion years old, leading scientists to speculate that life on the moon ceased at that time. But through the study of basalt in lunar samples from Chang'e-5, researchers have found that these basalts were formed by volcanic eruptions 1.96 billion years ago, making them the youngest lunar basalt discovered so far. That is to say, the magma activity on the moon may have continued until 1.96 billion years ago. Researchers point out that compared to the research results of the Apollo samples, the known geological lifespan of the moon has been extended by about 1 billion years. The research on Chang'e-5 samples not only rewrote the lifespan of the moon, but also answered another question that people are very concerned about - whether there is water on the moon. Researchers have conducted research on pyroxene, olivine, and plagioclase minerals in the lunar soil of Chang'e-5 and found that there is a large amount of solar wind induced water in the surface of Chang'e-5 minerals. It is estimated that the water content contributed by solar wind proton injection to the lunar soil of Chang'e-5 is at least 170 ppm (i.e. 170 parts per million), which is equivalent to at least 170 grams of water per ton of lunar soil. Further research has found that these solar wind induced waters can be well preserved in mid to high latitude regions of the lunar surface, confirming that lunar surface minerals are important reservoirs of water and providing important references for the distribution of water in mid latitude regions of the lunar surface, which is of great significance for the utilization of lunar water resources. In the future, we will establish an international lunar research station on the moon to achieve long-term human presence and work on the moon. The benefits of developing and utilizing water resources on the moon are obvious. In addition, there are more research achievements that have broadened and deepened our understanding of the moon: researchers have discovered a new mineral in lunar soil and named it "Chang'e Stone". This is the sixth new mineral discovered by humans on the moon, and China has become the third country in the world to discover a new mineral on the moon. ——Researchers have established the optimal temperature parameters for extracting helium-3 from lunar soil by heating it up in stages. As a potential nuclear fusion fuel, helium-3 is considered a future energy source. These key scientific data provide fundamental support for estimating the total amount of helium-3 resources on the moon in the future, as well as for the exploration and development of helium-3 resources. ——For the first time, researchers have discovered naturally formed graphene in lunar soil samples, broadening our understanding of the complex mineral composition of lunar soil and providing important information and clues for the in-situ resource utilization of the moon. Graphene plays an important role in a wide range of fields, including planetary and space science, due to its unique physical properties. The scientific research achievements are very rich Li Chunlai, deputy chief designer of Chang'e-6 mission and researcher of the National Astronomical Observatory of the Chinese Academy of Sciences, said that in such a short time, more than 100 high-quality papers on lunar soil research have been published, and some achievements have been published in international academic journals such as Nature and Science. At present, China has initiated the first international application and evaluation of lunar samples for Chang'e-5. In the near future, we may also receive surprises from the foreign scientific community. The lunar samples from Chang'e-5 will provide us with a more complete understanding of the moon, revealing so many mysteries about the moon. This makes us even more excited about the lunar samples from Chang'e-6. In the past, we only recognized half of the moon from the samples we collected Li Chun said that lunar samples from the far side of the moon are expected to provide an opportunity to study the binary nature of the moon and gain a complete understanding of its history. The reason why Chang'e-6 chose to sample in the South Pole Aitken Basin on the far side of the moon is to collect lunar samples that are as different as possible from the past, in order to study the moon more comprehensively. Compared to the front of the moon, the back of the moon has more impact craters and a smaller lunar mare range. Moreover, the moon's back undulates greatly, the terrain is higher, and the ground is rougher. During the sampling process, we felt that the lunar soil on the far and near sides of the moon was different. The soil on the near side was more delicate and loose, while the state on the far side seemed to be different Hu Hao said. Li Chunlai pointed out that the South Pole Aitken Basin is the largest, deepest, and oldest known basin on the moon, and its mineral chemical composition may differ greatly from that of the front. Studying the geological composition, material composition, and evolutionary history here helps to understand the geological evolution history of the moon, reveal the unique geological structures and differences in material composition on the far side of the moon, and gain a more comprehensive understanding of the geological evolution history of the moon. Since it comes from the oldest basin on the moon, it is highly likely that ancient materials from the moon will be discovered in the Chang'e-6 samples. Yang Yi, an expert from the Institute of Geochemistry of the Chinese Academy of Sciences, pointed out that according to the statistical dating of the impact crater, the Antarctic Aitken area is about 4.2 billion years old and may have the oldest rocks on the lunar surface. The youngest basalt on the moon has been discovered in the Chang'e-5 sample. Can the Chang'e-6 sample discover the oldest rocks and dating minerals on the moon? In addition to searching for the oldest rocks, Chang'e-6 samples may also discover deep lunar material. The Apollo impact crater where Chang'e-6 landed is located inside the South Pole Aitken Basin and is a "basin within a basin" formed by multiple impacts. Experts believe that this may be one of the thinnest locations on the lunar crust, a potential exposure area for deep lunar material, making it easier to obtain deep lunar material. Deep matter is very precious and difficult to obtain Li Chun said that the Chang'e-6 sampling point was ejected by early impact events, and it is likely to collect samples from the deep part of the moon, even the lunar mantle, providing valuable data for studying the internal structure and material composition of the moon. Moreover, lunar samples from impact craters can provide opportunities for studying the early impact history of the moon and even the early impact processes of Earth, helping to understand the early evolutionary history of the solar system and promoting comparative planetary studies.
Edit：He Chuanning Responsible editor：Su Suiyue
Source：Xinhua
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