"For example, mountains, rivers and even cliffs and volcanoes on Earth, many belong to the formation of the Earth's stress." Because the moon has no atmosphere on its surface, geological formations formed during its 4.5 billion years of evolution have been preserved to the maximum extent possible. These structures provide the temporal and spatial distribution of deformation or displacement of rock strata or rock masses during evolution.

Internationally, there have been no separate geologic maps of the Moon. According to Lu Tianqi, a member of Chen Shengbo's team and a doctor from Jilin University who is now an engineer with the China Geological Survey, in the 1960s and late 1970s,

the United States conducted a survey of lunar geology through the Apollo lunar landing program and drew corresponding maps, "but those maps only expressed some scattered types of lunar geological structures, and they were not systematic." Nor is it a specific geological map."

At the same time, because different cartographers have different understandings of the structure of their cartographic regions, the phenomenon of "homonyms" or "homonyms" often occurs, which leads to the confusion and misunderstanding of the structure.

In 2020, the United States released a full moon geological map composed of six 1:0.5 million scale lunar regional geological maps, but the geological map mainly shows lunar crater materials and basalt units, only showing a few structural types, and does not reflect the deep structure and small-scale structure of the moon.

In 2012, thanks to the support of the probe data of the Chang 'e project, China has the conditions to accurately identify the lunar structure. In this context, Jilin University, as the leading unit and a number of units within the United Nations,

has established a set of lunar structure classification system based on dynamic mechanism based on Chang 'e project data and other international lunar exploration data and research results.

"We combined the moon's geophysical, geochemical, topographic and structural distribution characteristics to divide five tectonic units. The outline map was completed by developing the standards, procedures, methods and illustrations for compiling the outline map of the lunar structure." Chen Shengbo said.

'Dynamic Display' of Lunar structure

The reason why the word "outline" is added to the name of the structure map published this time is because due to scale restrictions, some structures on the surface of the moon that are smaller than a certain scale are not reflected in the map. But even so, the content displayed is already very rich.

According to Chen Shengbo, the structural elements of this outline map mainly involve 9 types of linear structures, including speculated deep faults, shallow faults, crease ridges, moon streams,

moon grabens, pit bottom faults, leaf scarps, impact faults and impact crater chains; 5 types of ring structures, including crater, dome, mass nodules, impact crater, impact basin;

Five structural units, including three primary structural units and three secondary structural units, as well as landing sites, special place names and other special elements, the total number of structural elements more than 20,000.

"To show so much information in a single map requires the use of remote sensing technology to obtain a large amount of data about the geological structure of the moon, and the combination of multiple data analysis."

That's the biggest challenge of the job." Chen Shengbo introduced that many of the data involved the deep structure of the moon and could not be directly reflected, so a large number of complex modeling calculations were needed. "It's like taking a full-body CT of the moon."

However, this "CT picture" is not a simple "photograph", but a "dynamic display" of the evolution of the lunar geological structure.

Lu Tianqi explained that the research results are mainly composed of two parts, in addition to the static outline map, also includes a special network platform under construction. When completed, the platform will show the evolution of the moon's structure to the public.

In the process of drawing the outline map, the research team invited experts to carry out special legend design for the structure reflected in the map, and strive to show the evolution process of different structures.

"That is, we set up a specification that colors the different ages of the moon's geologic formations to distinguish when a certain formation was created and to show its evolution on a single map." Lu Tianqi said that because of this, the outline map will be extremely important for the study of the overall evolution of the moon.

It has multiple values for space exploration

In fact, regardless of scientific research, just in terms of "practicality", the success of the outline map is also of great value.

For example, whether it is a manned lunar landing or the establishment of a lunar scientific research base in the future, the first issue to be considered in the location of the landing area or construction area is whether the terrain is stable, and whether the lunar shell structure is stable. These are closely related to the geological structure of the place.