The water of the moon “comes from the sky”?

　　Some time ago, because Chinese scientists found a high content of water in the lunar soil minerals brought back by “Chang’e-5”, news about water on the moon was once again on the hot search. In fact, human beings have been exploring the water on the moon for a long time, and have gained a lot during the exploration process. Why do humans want to detect water on the moon? Where did the moon’s water come from? What is the use of the water of the moon? With these questions in mind, let’s talk about the water on the moon today.
　　The history of the discovery of water on the moon
　　Although astronomers have long discovered that the environment on the moon is far less beautiful than we imagined, the real moon is a planet without an atmosphere and full of craters, but this does not affect people’s attention to it. People have always wanted to find answers to some questions on the moon, such as whether there are water resources on the moon that have caused endless debate in the academic community. To put an end to the debate, many probes were sent to the moon.
　　Although during the space race between the United States and the Soviet Union, scientists have found the presence of water in the lunar soil samples brought back by the probe, but because the content of water detected from the samples is very low, and it is impossible to prove whether the samples were contacted on the way back. When it comes to water vapor, these discoveries about water on the moon cannot prove that water resources really exist on the moon. Similarly, the “Clementine” probe launched by the United States in 1994 and the “Lunar Prospector” launched in 1998, the detection results of water on the moon obtained by them were not widely accepted for some reasons.
　　After that, with the development of science and technology and the increase of detection efforts, the truth about the water on the moon gradually surfaced. In 2008, the “Chandrayaan-1” equipped with two detection artifacts, a micro-synthetic aperture radar and a lunar mineral mapper, was launched into space. After full analysis and verification of its detection results, scientists confirmed the fact that there is water ice on the moon. ; In 2020, NASA announced that the flight observation results of the Stratospheric Infrared Astronomy Observatory in 2018 proved that water molecules existed on the surface of the moon; Traces of water have been found on the moon.
　　But it needs to be explained that the water on the moon discovered by scientists is not the free liquid water or ice that we usually see, but water molecules or the main element that constitutes water molecules-hydroxyl.
　　Conjecture on the source of
　　water on the moon Although the detection results of the probe put an end to the debate on the existence of water on the moon, it also triggered a new debate-where did the water on the moon come from? At present, there are mainly three speculations about the source of the moon’s water.
　　No.1 comes from a comet. Many comets
　　have visited the moon. When the aliens hit the surface of the moon these days, although most of the water will evaporate, some of it may seep into the lunar soil and be preserved, becoming the water of the moon. In 2011, when American researchers analyzed the lunar surface rock samples brought back by the “Apollo” spacecraft, they found that the hydrogen isotope composition ratio of a type of mineral called apatite was the same as that of three known comets. The ratio of hydrogen isotopic composition is close. The findings raise the possibility that the moon’s water came from a comet.
　　No.2 from the solar wind
　　The solar wind may also be a major source of water on the moon. We know that the formation of water requires two elements, hydrogen and oxygen, but the hydrogen content in the original lunar soil is extremely low, and a large amount of oxygen exists in the lunar soil minerals. The solar wind blowing from the sun contains a large amount of hydrogen. When the solar wind blows to the surface of the moon, the hydrogen it brings may enter the lunar soil minerals and combine with the oxygen inside to form hydroxyl or even water molecules. preserved in the soil.
　　No.3 comes from the moon itself
　　Of course , it is not ruled out that the lunar soil already contains water. Previously, when researchers were studying lunar samples brought back by the “Apollo” spacecraft, traces of water were found in some minerals. China’s “Chang’e-5” probe also found traces of water in a piece of moon rock after landing on the surface of the moon. This lunar rock was originally located in the depths of the moon and was splashed onto the lunar surface during a meteorite impact. The discovery raises the possibility that the lunar water came from the moon itself.
　　Uses of the Water of the Moon
　　Water is the source of life. Many people may think that the purpose of scientists investing a lot of manpower and material resources to find water on the moon is to establish a human settlement on the moon, but this is not entirely the case. Because the lunar environment is very harsh, and the temperature difference between day and night exceeds 300°C, such an environment is not suitable for living. Therefore, even if drinking water resources for human beings are found, the possibility of emigrating to the moon is very small.
　　One of the main purposes of scientists searching for lunar water is to develop and utilize lunar resources. Water resources can produce liquid hydrogen and liquid oxygen after electrolysis, which can be used to prepare more efficient rocket fuel. If people can find enough water resources on the surface of the moon in the future, they can build small bases to store resources on the moon. At that time, humans could use the moon as a transit point to other planets for supplies on it.
　　Knowledge
　　link Magical compounds in lunar soil
　　In addition to water resources, there are many other valuable resources that can be used on the moon, such as some active compounds that exist in lunar soil.
　　Not long ago, Chinese scientists discovered some active compounds with good catalytic properties in the lunar soil brought back by “Chang’e-5”. Using these active compounds as catalysts, they successfully converted water and carbon dioxide into oxygen, hydrogen, methane and methanol with the help of simulated sunlight. This research result gave Chinese scientists a long-term plan. In the future, it may be possible to use the extremely low temperature of the moon at night to separate carbon dioxide from the air humans breathe, and then use sunlight and catalytic lunar soil to separate carbon dioxide. and water resources on the lunar surface into oxygen, hydrogen, methane and methanol.
　　If this plan can become a reality, in the future, local materials can be obtained on the moon to provide life support and fuel for astronauts, which will greatly reduce the load and cost of spacecraft. Of course, whether this plan can really become a reality still needs a lot of verification. Expect scientists to bring us more surprises.