What samples did Chang 'e V, which successfully returned to Earth, bring back?

In June 5438+February 65438+2 am in July 2020, Chang 'e V officially ended its space travel and returned to Earth smoothly. 165438+1At 4: 30 on October 24th, the Long March V rocket blasted off from Wenchang launch site in Hainan, sending the Chang 'e V probe to the moon. 65438+February 1, successfully landed on the moon, becoming the third probe in China to soft land on the moon. From launch to final loading and recycling, Chang 'e V ended its 23-day space journey and successfully completed China's first lunar sampling return mission with 2 kilograms of lunar soil samples. Chang 'e V landed at the Lion King Landing Site in Inner Mongolia. According to Modern Express, a professor from the School of Cosmos of Nanjing University of Aeronautics and Astronautics said: "There are strict conditions and requirements for spacecraft recycling, and it is not necessary to drop it wherever you want."

According to the characteristics of spacecraft orbit, the landing site must meet four basic conditions at the same time. Spacecraft will fly over the area many times. This place should be spacious. The terrain should be flat and the surface should be hard enough. Fourth, the meteorological conditions in this area should be good. At present, the United States mainly chooses to land on the sea, while Russia and China decide to land on the vast prairie. The Lion King Banner Space Landing Site in Inner Mongolia is located in Jiulang Grassland, A Mu, Central Inner Mongolia, and is the most important space landing site in China. From the owner 1 to the owner 1 1, they all landed successfully here. The grassland is between 65,438+0,200m0 m and 65,438+0,200 m above sea level, with flat terrain, high bird's eye view and sparsely populated, with a population of no more than 65,438+00 per square kilometer, which is suitable for spacecraft landing.

The Chang 'e V returner returned to Earth in the form of "bouncing and re-entry". This form of regression has a popular metaphor-"things drifting in the universe". This method is adopted because the highest speed of the returner reaches11.2km per second in the process of flying 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 difference of 3.3 km/s will bring a very high temperature difference. If the Chang 'e V reentry vehicle chooses "hard ram" (i.e. ballistic reentry) and enters the earth's atmosphere at the speed of 1 1.2km/s, it will face the test of extreme high temperature. Because the attitude and orbit cannot be controlled, the ability of orbit design, separation and release and impact prediction is very high.

Chang 'e V returner finally chose the way of "bouncing and re-entering". According to Beijing Daily, Meng, chief designer of Chang 'e-5 probe, explained: "The returner first enters the atmosphere at high speed, then passes through the atmosphere with the help of 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 in 15 minutes. " This requires a special design for the returner. According to the report of the Central Broadcasting Network, Liu Hai, deputy director of the Chang 'e-5 probe returner, said: "The returner is like an oyster digging a hole in the side, and there is a hole in the hole that we call a propeller." "When the returner flies in the atmosphere, it not only suffers from resistance, but also produces a certain lift. Relying on this lift, the returner can successfully realize the rebound path. The return speed of Chang 'e V is very fast, and the surface temperature can reach 2000 degrees Celsius. If the heat cannot be stopped, the temperature will affect the lunar soil, and the returner will burn in the high-speed friction of the atmosphere.

The returner adopts rebound and jump reentry mode to reduce the speed and friction temperature. However, in this way, the returner needs to go through the changes of high temperature, low temperature and high temperature again, and the heat dissipation technology needs to be further tested, so the researchers put on the "heat dissipation suit" for the returner. In particular, the returner adopts honeycomb structure heat dissipation layer, filled with new anti-ablation materials and designed with new heat dissipation structure. According to Beijing Daily, the researchers put forward the specific requirements and indicators of ablation resistance and heat insulation for different parts of the lunar orbit to meet the requirements of returning thermal environment, space environment and weight, and selected 7 kinds of heat dissipation materials from 33 new research materials, and completed the layout of heat dissipation materials and the design of local heat dissipation structure. The heat dissipation structure design of China re-entering deep space orbit from near-earth orbit is realized.

Chang 'e V brought 2 kilograms of lunar soil samples this time, some of which were kept in Beijing and some in Hunan. Wei Wu Personnel Company, the chief designer of China's lunar exploration project, said that the lunar samples brought back from the moon by Chang 'e V will be preserved in two parts. It is said that one will be in Beijing and the other will be in Hunan. Chairman Mao said "but Range Rover No.9", and now we have realized "Range Rover No.9". Therefore, putting the moon soil in Hunan is also a comfort to Chairman Mao. The greatest function of lunar soil is to help scientists analyze the surface structure, physical characteristics and material composition of the moon, deepen the research on the origin and evolution history of the moon, and explore ways for human beings to understand and develop lunar resources.

According to Changsha Evening News, Liu Tianxi, Minister of Exhibition Department of geological museum, Hunan Province, said that both lunar soil and soil are weathered by rocks, but their compositions are different and they belong to two completely different soils. Moonlight is composed of minerals (such as olivine and plagioclase). ) and vitreous body. The soil composition on the earth is mostly organic matter, humus, water and so on. The place where Chang 'e V sampled from the moon is a relatively flat area near Ramke Mountain. In order to obtain moon samples with unique scientific value, it is necessary to avoid the sampling areas of the United States and the former Soviet Union. The history of basalt and volcanic activity in Ramke Mountain area is much younger than the landing sites of the United States and the former Soviet Union, which lasted about 65.438+0.3 billion-2 billion years. The landing sites chosen by the latter are all over 3 billion years old.

After studying the moon samples brought by the United States and the former Soviet Union, scientists found that lunar volcanic activity reached its peak 3.5 billion years ago, and then gradually weakened and tended to stop. However, other features on the surface of the moon indicate that some parts of the moon may contain volcanic lava formed 65.438 billion to 2 billion years ago. When exactly did the lunar volcanic activity stop? The samples collected by Chang 'e V near Ramke Mountain may answer this question. In addition, there is no liquid water on the moon, but solid water is not excluded. At present, the United States and the Soviet Union have not found the composition of water after studying the moonlight collected on the moon. If water can be found in the moonlight collected by Chang 'e V, it will be a major breakthrough.