In nine days, the moon and stars are wide, and the sixteenth spring and autumn fall back.
On November 17, the Long March 5 Yaowu carrier rocket and the Chang'e-5 probe, known as the "Fat Five", completed the assembly and testing of the technical area at the Wenchang Space Launch Site in China, and were vertically transported to the launch area, which is scheduled for November. In the second half of the year, we choose the opportunity to launch.
Image source: China National Space Administration
The Chang'e-5 lunar probe plan for the first time realizes the sampling and return from the moon, bringing valuable samples such as lunar soil or lunar rock back to the earth, and it is expected to be the three steps of "wandering, falling and returning" for the major scientific and technological projects of my country's lunar exploration project. Take the development strategy and draw a successful conclusion.
The average one-way distance between the earth and the moon is about 380,000 kilometers, and a round trip is nearly 800,000 kilometers. What are the mysteries in the lunar samples worthy of such laborious exploration?
Looking back at history, what achievements have mankind made in going to the moon to "dig earth"?
What are the special features of my country's Chang'e-5 mission from sampling location to sampling weight?
Although the lunar soil is soil, it is worth ten thousand gold
"The lunar soil is the soil of the moon. Although it is readily available on the moon, it has great scientific value for the people on earth." said Xiao Long, a professor at the Institute of Planetary Science of China University of Geosciences (Wuhan). Lunar soil studies the moon. The sample is formed by the lunar rock being subjected to meteorite impact, solar wind bombardment and cosmic ray radiation and other space weathering effects, including a large number of lunar rock fragments, minerals and meteorites.
By studying these lunar soil materials, scientists can not only understand the geological evolution history of the moon, but also provide necessary information for understanding solar activities.
"There are three common methods for detecting the moon." Pang Zhihao, the chief science communication expert of national space exploration, told the reporter of Science and Technology Daily. One is surround detection, which is mainly used for comprehensive survey of the moon; the other is landing and patrol detection, which is mainly used for moon detection. Carry out a regional detailed survey; the third is the sampling and return detection, which is mainly used for a regional survey of the moon.
Compared with the first two methods, sampling and return detection can transport key samples such as the lunar soil of the moon back to the ground laboratory for scientists to conduct accurate analysis and research, which is conducive to further understanding of important information such as the state, temperature, and material content of the moon. Understanding of the formation and evolution of lunar soil, lunar crust and moon.
Pang Zhihao said that from a technical perspective, the three space exploration methods have an obvious progressive relationship. Each step is a deepening of the previous step and at the same time lays the foundation for the next step, ultimately achieving the goal of a comprehensive and in-depth understanding of the moon.
Completing the mission of sampling and returning to the moon requires a comprehensive, detailed and in-depth scientific exploration process, which can break through a series of key technologies, and provide relevant data and lay the technical foundation for future manned moon landings and moon base site selection.
"Digging" is attractive, and all countries work hard
"During the Cold War, the United States and the Soviet Union, the space superpowers at that time, were keen to sample on the moon." Pang Zhihao said that the Soviet Lunar 16 probe retrieved a small sample of 101 grams from the lunar fertility sea.
The Lunar 20 probe and the Lunar 24 probe collected 55 grams and 170 grams of samples from the Apollonius Highlands and the Lunar Sea respectively.
"The manned spacecraft sampled and returned from the moon, not only has a large collection volume and a strong selectivity, but also a wide range of collection, because the astronauts can go to extravehicular activities and can also take the lunar rover to roam far away to collect lunar samples. For example, the geographic distribution and geological features of the sampling locations of the Apollo missions in the United States are very rich." Pang Zhihao said.
From July 1969 to December 1972, the United States carried out 7 manned missions to the moon through the Apollo 11 to Apollo 17 manned spacecraft. Except for Apollo 13 which returned midway due to a failure, the remaining 6 spacecrafts were all The moon landing was completed and 12 astronauts were successfully sent to the moon, bringing back a total of 381.7 kilograms of lunar soil and lunar rock samples.
According to reports, Apollo 11 landed in the quiet sea near the moon's equator. The reason for choosing this location is that it is relatively flat, which is convenient for the landing of the spacecraft and the extravehicular activities of the astronauts.
Both Apollo 12 and Apollo 14 landed on the moon’s equatorial plain. The former landed in the Sea of Storms, and the latter landed at Copernicus crater located 177 kilometers to the right of the Apollo 12 landing site.
Apollo 15 landed at the foot of the Apennines southeast of Archimedes crater in the central northern hemisphere of the moon, and Apollo 16 was the first time humans landed near Theophilus crater in the central highlands south of the moon's equator.
Apollo 17 landed in the Taoles-Littrow Valley in the northern hemisphere of the moon, where younger rock samples can be collected from the bottom of the valley, or older rock samples can be collected from the lunar highlands.
Image source: Visual China
"Through the analysis of lunar samples, scientists have achieved fruitful results." Pang Zhihao said, researchers have found through research that the lunar soil contains a large number of tiny orange-red glass particles, which are generally rich in aluminum, sulfur and zinc. They were formed at a depth of about 300 kilometers below the surface of the moon during the partial melting of the moon's mantle, and were ejected onto the surface of the moon due to volcanic activity.
The analysis and experiments on the samples confirmed that the iron oxide content in the lunar soil and moon rock is very high, from which water and oxygen can be produced. In the future, lunar materials can be used to support the operation of the lunar base and supplement fuel for the lunar landing vehicle.
More importantly, scientists also discovered helium-3, an ideal raw material for nuclear fusion, in the collected samples.
According to the current scale of the earth's energy consumption, helium-3 on the moon can meet human energy needs for about 10,000 years after being used for nuclear fusion power generation.
Chang'e has its own characteristics and new location
"my country's Chang'e-5 has a stronger ability to sample the lunar soil." Pang Zhihao said that the three unmanned lunar probes of the Soviet Union Lunar 16, Lunar 20 and Lunar 24 conducted three lunar sampling and return missions and brought back the moon. The soil sample is only about 330 grams, and my country only plans to bring back 2 kilograms of lunar samples from the Chang'e-5 probe.
According to Pang Zhihao, the significant difference in sampling weight was because the Soviet Union had not yet mastered the lunar orbit unmanned rendezvous and docking technology, so its three unmanned lunar sampling missions adopted the scheme of taking off from the moon and returning to the earth directly. The ascender needs to overcome the huge load brought by the return cabin and a large amount of fuel, so the sample weight is greatly compressed.
The Chang'e-5 plan uses the world's leading lunar orbit unmanned docking program to transfer the lunar soil. The ascender does not need to carry the return capsule, and only needs a small amount of fuel, so the sample weight is increased geometrically.
According to related reports, the sampling site of Chang'e 5 is also very distinctive and has high research value.
Chang'e-5 will land near the Rumke Mountains in the northern part of the Moon Sea Storm Ocean, the largest on the front of the moon, where no probes from other countries have ever visited.
The storm ocean is relatively young and is rich in radioactive elements such as uranium, thorium, and potassium. There are basalts about 1.3 to 2 billion years ago in the area. Obtaining the isotope age of these young basalts will help promote the evolution and evolution of the moon. Awareness of history.
As stated in the article in the top international scientific journal "Nature" on November 5, Chang'e-5 can fill an important gap in the study of lunar volcanic activity by scientists.
Previous studies of lunar soil samples obtained by the United States and the Soviet Union have shown that volcanic activity on the moon peaked 3.5 billion years ago, then weakened and stopped.
However, observations on the surface of the moon have found that some areas may contain volcanic lava formed only 1 to 2 billion years ago, which is similar to the age of the Chang'e 5 landing area.
If the samples collected by Chang'e-5 can confirm that the moon is still active during this period, it will rewrite the history of the moon.
(Intern reporter Yu Ziyue)