What samples did Chang'e-5 bring back to Earth successfully?

At about 2 o'clock in the morning on December 17, 2020, Chang'e 5 officially ended its space travel and successfully returned to Earth. At 4:30 on November 24, the Long March 5 Long-range 5 rocket lifted off from the Wenchang launch site in Hainan, sending the Chang'e 5 probe to the moon. On December 1, it successfully landed on the moon, becoming China's third probe to soft-land on the moon. From launch to final loading and recovery, Chang'e 5 ended its 23-day space journey and successfully completed China's first lunar sampling return mission carrying 2 kilograms of lunar soil samples. Chang'e 5 landed at the Lion Air Landing Ground in Inner Mongolia. According to Modern Express, a professor at the School of Astrology at Nanjing University of Aeronautics and Astronautics said: "The recovery of the spacecraft has strict conditions and requirements, and it will not land where you want it."

According to the characteristics of the spacecraft's orbit, the landing site Four basic conditions must be met at the same time. The spacecraft will pass over the area multiple times. The place should be spacious. The terrain should be flat and the surface should be hard enough. Fourth, the meteorological conditions in the area must be good. At present, the United States mainly chooses to land at sea, and Russia and China have decided to land on the vast steppes. The Inner Mongolia Lion King Banner Space Landing Site is located on the Amujiulang Prairie in central Inner Mongolia. It is the most important space landing site in China. Shipowner No. 1 to Shipowner No. 11 all successfully landed here. The grassland has an altitude between 1,000 meters and 1,200 meters. It has flat terrain, high air visibility, sparsely populated areas, and a population of no more than 10 people per square kilometer. It is suitable as a landing site for spacecraft.

The Chang'e 5 returner returned to Earth in an "anti-trajectory jump reentry" method. This form of return has a popular metaphor - "cosmic matter drifting". The reason for this method is that the return vehicle reaches a maximum speed of 11.2 kilometers per second during its flight from the moon to the earth, which is already the second cosmic speed. The spacecraft returning from low-Earth orbit is about 7.9 kilometers per second, which is the first cosmic speed. This 3.3 km/second difference will bring about a very high temperature difference. If the Chang'e 5 returner chooses "hard stamping" (i.e. ballistic re-entry) and enters the Earth's atmosphere at a speed of 11.2 kilometers per second, it will face the test of extreme high temperatures. Since it cannot control the posture and orbit, it will have serious consequences for orbit design, separation release and The requirements for impact point prediction capabilities are very high.

The Chang'e 5 returner finally chose the "anti-trajectory jump reentry" method. According to the "Beijing Daily" report, Meng Zhanfeng, chief designer of the Chang'e 5 probe, explained: "The returner first enters the atmosphere at high speed, then crosses the atmosphere with the lift provided by the atmosphere, and then enters the atmosphere at the first cosmic speed and returns to the ground. The whole process is interlocking and completed within 15 minutes. "With this return method, the return device needs to be specially designed. According to the Central Optical Network, Liu Hai, deputy chief designer of the returner of the Chang'e 5 probe, said: "The returner is like an oyster with a hole dug on the side. In the hole is what we call a propeller hole." "When flying in the atmosphere, The returner not only experiences resistance, but also generates a certain amount of lift. By relying on this lift, the returner can successfully achieve the anti-trajectory jump method. The return speed of Chang'e 5 can reach 2000 degrees Celsius. If the heat cannot be prevented, the temperature will increase. Passing into the interior will affect the lunar soil, and the returner can also burn in the high-speed friction of the atmosphere.

The returner uses an anti-trajectory jump reentry method to reduce the speed and friction temperature. , the returner needs to experience changes in high temperature, low temperature and high temperature again, and further experiments on heat dissipation technology are needed, so the researchers put on a "heat dissipation suit" on the returner. In particular, the returner uses a honeycomb structure heat dissipation layer, which is filled with new ones. The ablation-resistant material adopts a new heat dissipation structure design. According to the "Beijing Daily" report, in response to the thermal environment, space environment, and weight requirements of the lunar orbit, researchers have proposed specific ablation resistance and heat insulation for different parts. requirements and indicators, and selected 7 types of heat dissipation materials from 33 new research materials, completing the layout of heat dissipation materials and the design of local heat dissipation structures to achieve China's heat dissipation structure design for re-entering deep space orbit. p>

Chang'e 5 brought 2 kilograms of lunar soil samples this time, some of which will be placed in Beijing and some of which will be stored in Hunan. Wu Wei, chief designer of China's Lunar Exploration Project, said that Chang'e 5 The Yueyang samples brought back from the moon will be divided into two storages, one will be stored in Beijing and the other will be stored in Hunan.

Chairman Mao said "But Range Rover No. 9", and now we have achieved "Range Rover No. 9". Therefore, placing lunar soil in Hunan was also a comfort to Chairman Mao. The biggest role of lunar soil is to help scientists analyze the structure, physical properties and material composition of the lunar surface, deepen the study of the causes and evolutionary history of the moon, and explore ways for humans to understand and exploit lunar resources.

According to the Changsha Evening News, Liu Tianxi, the director of the Hunan Geological Museum’s display, said that both lunar soil and earth soil are weathered from rocks, but their compositions are different and they belong to two complete Different soils. The components of Yueyang are minerals (such as olivine, plagioclase, etc.) and glass. The soil components on the earth are mostly organic matter, humus, water, etc. The place where Chang'e 5 sampled from the moon was a relatively flat area near Mount Ramko. In order to obtain lunar surface samples of unique scientific value, areas sampled by the United States and the former Soviet Union must be avoided. The history of basalt and volcanic activity in the Mount Ramko area is much younger than that of the landing sites of American and former Soviet landers, lasting about 1.3 billion to 2 billion years. The landing sites chosen by the latter are all more than 3 billion years old.

After studying lunar samples brought by the United States and the former Soviet Union, scientists found that lunar volcanic activity peaked 3.5 billion years ago, then gradually weakened and tended to stop. But other features on the moon's surface suggest that parts of the moon may contain volcanic lava that formed between 1 billion and 2 billion years ago. When did lunar volcanic activity stop? Samples collected by Chang'e 5 near Mount Ramke may be able to answer this question. In addition, there is no liquid water on the moon, but solid water cannot be ruled out. At present, the United States and the Soviet Union have found no water content after studying the lunar sun collected on the moon. If water can be found in the moon collected from Chang'e-5 this time, it will be a major breakthrough.