In the Spirit of Science, Do Professional Work－An Interview with CAE Academician ZHAO Wenjin

CAI Ting

China Aerospace Academy of Systems Science and Engineering, Beijing 100048

CAE Academician ZHAO Wenjin

On November 7, 2005, the Lunar Exploration Scientist Team (the Team) under the Ministry of Land and Resources(MLR) was formally established with thefirst members being 7 scientists including ZHAO Wenjin. Later Dr. YANG Hongwei was appointed as the academic secretary. The Team has been committed to China's lunar exploration activities and strengthen cooperation to enable MLR to fully benefit from national lunar and deep space exploration.

At the Chinese Academy of Geological Sciences, journalists fromAerospace Chinavisited academician ZHAO Wenjin,a member of the Chinese Academy of Engineering (CAE)and an expert in Earth exploration and comparative planetary science, and discussed the dialectical development relationship between Chinese deep space exploration and multi-disciplinary integration.

· First of all, could you let us know about your team's contribution to the national lunar and deep space exploration programs?

Academician ZHAO Wenjin: In view of numerous data on international lunar and deep space exploration, and scientific cooperation with the USA in deep space exploration, we decided to apply the lunar exploration data in deep space exploration,obtaining also some previous data through exchanges with international scholars and universities. With the focus on planetary science and lunar resources research, we have supported the relevant departments for lunar and deep space exploration from a scientific perspective.

First of all, we investigated the progress in international lunar exploration during the 20th century, summarized the major scientific issues and took them as the starting point for our lunar exploration.

We jointly translatedNew Views of the Moon(720 pages) into Chinese(Figure 1) with American counterparts and published it in May 2012. This summarizes the international lunar exploration progress by the National Aeronautics and Space Administration(NASA) and European Space Agency(ESA), and the English version was published in the USA in 2006. During the translation and research summary, I further supplemented and developed the nine scientific issues identified in the book,and proposed the following 12 important scientific issues: the vertical and lateral structural changes of the lunar crust and its evolution; the relationship between material on the surface of the moon and its internal structure; the composition and structure of lunar mantle, and its geological features; the formation mechanism, size and distribution of the Magma ocean; the nature and causes of moon asymmetry;the distribution, origin and evolution of lunar mare volcano;the time of major impact events and the in fluence on the formation sequence of lunar crust; the property of Aitken Basin,Antarctica, and its in fluence on lunar evolution; the cause of lunar paleomagnetism; the major lunar resources; the existence of large volumes of water or other fluids on the moon or the occurrence of large-scale jet blast in the past; space weathering and impact events; the interaction of Earth and moon, and the impact of Earth on the moon; the major in fluences of moon in the Earth, especially Earthquake and atmospheric changes on the Earth, and the harm of celestial impacts to the Earth.

In June 2009, funded by China Geological Survey, an International Seminar on Lunar Exploration and Geosciences was held to discuss the relationship between lunar exploration and geoscience research, emphasizing that the moon is closest celestial body to the Earth.

Figure 1 Chinese version of New Views of the Moon

12 lunar scientists who represent the USA, Japan and India, participants in lunar exploration, attended this seminar and explained the phases of lunar exploration. After using astronomical telescopes and meteorites to observe and study the moon on the ground (Phase I), lunar orbiters were launched for remote sensing (Phase II), robots for lunar sampling (Phase III), and even astronauts made a lunar landing forfield investigation (Phase IV).

There was also published a report comparingfield observation with remote sensing. The advantages offield observation are as follows. First, is that the astronauts can collect as many samples of different significance duringfield investigation, as oppose to bulk sampling in one place. Second is that a geological profile can be mapped to link the sampling points on the lunar surface to the geological section, thus to further study samples in terms of space and time. In contrast, remote sensing cannot identify these relationships. Third is that the geological phenomena not observed by the remote sensing can be observed by astronauts. From the two photos in Figure 3, we can see the basalt stratification, which is probably the rooted protolith rather than an external object. This is very important.With a rooted rock, the absolute age of the sample, its lithology and sequence can be determined to accurately demonstrate the planets evolution. Therefore, the method of using the rate of meteorite impact to determine the age is completely improved. Unfortunately, we did not obtain any protolith samples during the previous nine lunar samplings. Fourth is that astronauts can make further geophysical (such as Earthquake,electrical and thermal measurements) and gas measurements,and geological observations on the lunar surface. Thus, the data at different depths below the surface can be obtained, and they are indispensable for the study of the lunar structure and evolution. Fifth is that astronauts can experience the moon living conditions. As human beings go to space, it is inevitable to make such transitional preparations on the moon. It was found that the lunar dust and space radiation are very dangerous to future space activities. Sixth is that in terms of technology,robots have great potential for landing on the moon. However manned observation has advantages in flexibility, professional breadth and depth, and discriminant analysis due to the new and complex environment on the moon.

Therefore, at Phase III and IV, it is necessary to apply the experience and knowledge of regional geological survey, geophysical and geochemical research from the Earth. The key research points at Phase III and IV are essentially different from that of Phase I and II. In particular, astronauts on the moon should have professional geological survey knowledge.In addition, it's necessary for geologists to participate in the exploration of the moon and other planets.

To further prepare for the scientific knowledge for Phase IV lunar exploration, the MLS has carried out seven projects,focusing on the study of the distribution of surface materials on the moon and mars, the high-precision lunar gravity map and its geological interpretation, seismological imaging research, preparation of lunar geologic maps, improvement of age determination techniques on lunar rock, deep structure and evolution of the moon, and the development of a lunar sampling rig.

(1) The age of lunar rock samples was measured. With the support of the Ministry of Science and Technology and with the cooperation with the University of Washington, we have conducted age determination of the Apollo 12 lunar sample A-12, the Apollo 14 lunar sample A-14, the zircon and phosphorite in lunar meteorite sample SaU169, and the U-Pb of merrillite, established the methodology, and obtained a total of 135 analysis results. This was measured by internationally recognized standard methods so that it is more authoritative.However, the lunar dating is still determined by the meteorite impact number, which is less reliable and needs to be further improved. There won't be an accurate concept of development and evolution without accurate dating.

(2) The distribution of nine elements and four minerals on the moon was determined and about 30figures were mapped.Using the lunar exploration from Chang'e 1, American Clementine and Indian M3, the nine elements were interpreted as ferrum, magnesium, aluminum, calcium, titanium, silicon,uranium, thorium and potassium. The four minerals were plagioclase, clinopyxene, orthopyroxene and ilmenite. In addition,these elements and minerals are regularly distributed.

(3) Remote sensing spectrum analysis of the lithology of 86 central peaks was conducted, aiming to identify lunar deep materials revealed by the central peak.

(4) Focus on how to improve the resolution data of the lunar gravityfield. The distribution of the gravityfield on lunar surface re flects the lunar mass distribution at a certain depth,and is the only data that can interpret the mantle change at the lunar crust. Only the gravity anomalyfield of about 50-order resolution can be obtained through the data from Chang'e.Dr. Yang Hongwei obtained a 53-order gravity map (an accuracy of 102 km) by a calculation method using the Japanese lunar exploration satellite and relay satellite. Take the Apollo crater on lunar far side as an example, the comparison of this result with the L165P model established by the USA Lunar Prospector is shown in Figure 2.

With the data from latest GRAIL gravity satellite launched by the USA, the GL0660B model was also established to analyze the distribution of gravity anomalies at different depths.The 150-order free air gravity anomaly fields of high spatial resolution on the moon, and the 330-order Bouguer gravity anomalyfield of 16 km resolution are obtained.

Figure 3 clearly indicates the high and low Bouguer and gravity anomalies. Among them, the Bouguer gravity anomaly in the oeanus procellarum and the Aitken Basin is the highest,while the gravity in the anorthosite is low compared with the high gravity locally. The distribution of different depth materials can be known. Meanwhile, the GL0660B model shows the high accuracy gravity anomalies on lunar farside at different heights, which can provide a basis for Chang'e 4 to land on the lunar farside for exploration.

Based on 24 high-accuracy (64 m grid) lunar topographic maps, the rift generated by impact craters and the moon itself can be identified. No large-scale linear mountain by the plate driving force on the Earth is found on the moon.

Figure 2 The 165-order gravity model (LP165P) established by the USA Lunar Prospector (left).

Figure 3 The 330-order Bouguer gravity anomalyfield on the moon

(5) An analysis of the causes of lunar geomorphology and the study of whether there has been large-scale water has been conducted. HAN Tonglin from the Geologic Institute in the Chinese Academy of Geological Sciences has studied the lunar geomorphology by compiling lunar geologic maps. From the lunar rille, sedimentary plains, sediment characteristics in the moon crater, alluvial fan distribution, the relations between mud cracks and gullies, Han boldly proposed that there has been a lot of water in the history of the moon. The existence of “water ice” is demonstrated by the geomorphological features such as frozen-melt mud, frost mound and frost heaving fissure, rock-block field, debris slope, stone ring, stalagmite, thermal erosion subsidence and thermal erosion slump.Though further verification is required, this idea is instructive.It involves the existence of large-scale water or fluids in the history of planets, a source of water and its later loss.

(6) We have designed a lunar sampling drill. Considering the low atmospheric pressure on the lunar surface, water-free,microgravity, high temperature and cold, the first lunar micro-drill in China was designed and manufactured for unmanned autonomous drilling on the moon. Particularly under the extreme environment where the lunar gravity is 1/6 of the Earth gravity, an impact function specially designed to increase the drilling pressure can increase the drilling power while reducing the weight of the whole machine.

(7) We have established a lunar test site in Liuyuan Gansu province. Established in an area on the Earth similar to the basalt area of the moon, the test site allows people to understand test results of remote sensing and geophysical methods in basalt areas, and provides a basis for geological interpretation of planetary exploration results. In this basalt analogy test site,artificial Earthquakes, radar detection, gravity and magnetic prospecting, and remote sensing observation have been carried out. The way to use this data to study the structural composition of a basalt area was also studied in combination with a geological investigation.

Figure 4 Lunar basalt test site in Liuyuan Gansu

(8) We have established a Mars test site in Dalangtan Qinghai province. It is considered as a test site closest to that of the Mars salt environment in the world. The halogen rocks on the mars were studied at this site, including the formation conditions for sulphate and carbonatite minerals as on the Mars surface. The possibility of organisms in a Mars salt deposition environment is discussed.

(9) With the support of relevant state departments, thefirst lunar surface geological map (1:2500000 Sinus Iridum) in China was compiled by the Mapping Office of Geological Institute, including Sinus Iridum (located in the northwest of the Mare Imbrium ), Mare Imbrium, Oeanus Procellarum, Sinus Roris and Mare Frigoris. The map was compiled for Chang'e 3 to land on the moon.

· Please give us some suggestions on China's lunar and deep space exploration for the future?

Academician ZHAO Wenjin: Combining with the extensive basic research by the MLS for deep space exploration over the past decade, I deeply feel that geological departments should be more actively involved in the national deep space exploration activities. On one hand, their technical and theoretical knowledge accumulated in the long term can be used to support the national deep space exploration activities. On the other hand, they can take the opportunity of deep space exploration to promote comparative planetary studies and further clarify using the Earth itself in the comparison.

I have three suggestions:

First, the lunar and deep space exploration activities are long-term national strategic activities. Space technology development and planetary and solar system research are also longterm activities. It is necessary to provide a long-term phased implementation scheme, personnel training and use schemes,and develop technology, equipment, goals. For this purpose,we should actively learn from the successful experiences in cooperation with and organize scientific and technological forces in scientific research institutions from the USA, Europe, Japan,India and Russia.

Second, the scientific and technological innovation in Chi-na's spacefield has yielded fruitful results, while the research on basic geoscience issues of planetary exploration is relatively weak. The four basic scientific issues in lunar research are the survey of moon status and it's resources, the evolution of the moon, and the relationship between the moon and the Earth.There is no specific state-level lunar exploration plan or clear scientific system. The scientific objectives and long-term planning of the mars exploration also lack in-depth demonstration.However, the solar system shall be studied as a whole, and the exploration results need to be linked and compared with each other. Each research system cannot be isolated and needs to advanced and be coordinated in a planned and systematic way,in order to ensure quality and efficiency, and prevent the fragmentation of scientific and technological achievements.

Third, the openness and social participation in scientific research is insufficient. In the USA space and deep space explorationfields, the technology is highly confidential, but the exploration data is open to the world, and scientists from all over the world are encouraged to use the data for relevant research.The USA space science community believes that the more indepth and extensive research on the data of planetary exploration, the more scientific benefits will be gained. Meanwhile, it will help popularize scientific and technological achievements to a high degree and attract the participation of the public.

· How should we turn a series of new technology industries into economic benefits through deep space exploration activities? How should we benefit the public by the scientific achievements and improve their scientific awareness?

Academician ZHAO Wenjin: As a scientific cause, the social effects of deep space exploration should be considered besides the short-term objectives and long-term plans.

For lunar and deep space exploration there is no doubt there will be valuable opportunities born for new technologies and industries. The USA space activities have fully demonstrated this practical significance.

The main purposes of all the USA space activities are to (1)clarify the theme and long-term objectives of the next 10-year planetary science research; (2) think about interdisciplinary studies in planetary science and human exploration activities in an international context; (3) study the exploration missions that can generate new scientific concepts based on scientific research objectives; (4) think about specific exploration techniques to achieve scientific goals; (5) identify challenges (e.g.measurement challenges, technical challenges, etc.) that require early investment to resolve.

Obviously, this plan is made based on an existing 10-year plan, with a highly consistent approach. That is to say, through multifaceted investigation and research of the solar system,people are encouraged to carry out a series of innovative activities in terms of ideas and technologies, some of which include basic research, but more of which are application-based research and development. This is a more meaningful science and innovation activity at the state level.

As one of the major powers that in fluence the international world pattern, whether China can grasp this rare opportunity to inspire people's innovation awareness and realize the dream of becoming a space power depends not only on the overall planning by the government, but also on coordination amongst all sides. We should absorb all referential, available and cooperative resources, fully tap into the social value of deep space exploration and its derivative activities, and set off an exploration fervor throughout China.

To become a technologically strong country is not a slogan on paper. There are different voices and positions in the path of science. As a far-reaching national strategic scientific research project and a national undertaking, more scientific,objective and a professional spirit is always in great need. China should take its responsibility as a great power to orderly implement this national cause, in order to stand in the forefront of the future space battle!

I hope that in this undertaking, both at the decision-making level and the scientific community level can adhere to a“scientific planning, systematic advancement, overall layout and goal-oriented spirit”.