Research On The Construction Of The Brokenness Index Of The Moon Surface Based On DEM And Its Spatial Differentiation Characteristics

As the only natural satellite of the earth,the moon has always been the first choice for human deep space exploration all the time.Since the 1960s,the acquisition of various lunar exploration data,represented by remote sensing image data and terrain data,has provided important data support for the study of lunar space environment,lunar surface topography characteristics and lunar tectonic evolution.In recent years,the digital elevation model(DEM)data obtained by laser altimetry has been widely used in the study of lunar surface topographic features and spatial differentiation characteristics because of its three-dimensional spatial expression ability and fine terrain analysis ability.The landscape fragmentation of terrestrial surface measures the fragmentation of terrestrial surface landscape under the interference of natural or human factors,and reflects the development and evolution characteristics of terrestrial surface landscape.As the most intuitive and typical morphological unit of the lunar surface,impact craters record the relatively complete impact history of the moon since its birth,and have become an important carrier for studying the development and evolution of the lunar surface morphological characteristics.Currently,the research on the morphological characteristics of the lunar surface based on the impact craters mainly focuses on the density index of the impact craters,which reflects the impact fragmentation degree of the specific areas of the lunar surface by showing the spatial concentration degree of the impact craters.However,in describing the degree of fragmentation of the lunar surface caused by impact bodies of different sizes,the density of impact craters only indicates the number of impact craters in a specific area of the lunar surface,which neglects the proportion of the area fragmented by impact,so it is difficult to visually reflect the degree of fragmentation of the lunar surface by impact.Therefore,this paper draws lessons from the theory and method of landscape fragmentation of terrestrial surface,defines the total area of impact craters in a specific area of the lunar surface as the index of lunar surface fragmentation based on the LU62287GT lunar impact crater database,which was built via the 100-meter resolution DEM data obtained by the Lunar Reconnaissance Orbiter(LRO),and studies the spatial differentiation characteristics of the index.The main conclusions of this study are as follows:1.In the process of building the database of lunar impact craters and the index of lunar surface fragmentation,the lunar impact craters can be divided into three main types,discrete impact craters,cluster impact craters and degenerate impact craters,and seven sub-types according to the spatial location and development of impact craters.Based on visual interpretation of impact craters by DEM and its derived topographic factors,the average diameter error of impact craters is 4.92 km,and the average error rate is 16.93%.The accuracy of extraction is over 77%and total extraction quality is more than 70%in automatic extraction of impact craters using linear window neighborhood analysis.When the scale of the sample area is between 22.5-36 latitude difference and 40-60 longitude difference,the value of lunar surface fragmentation tends to be relatively stable on the whole moon.2.The spatial difference between lunar surface fragmentation and density of impact craters indicates that the index of the lunar surface fragmentation constructed in this paper has certain indicative significance for the surface morphological characteristics within the whole moon.The prominent manifestations are as follows:in the polar regions,the luar surface fragmentation is the high value area,while the density of impact craters is the low value area;in the near equatorial region,the lunar surface fragmentation is the low value area,while the density of impact craters is the high value area.The results show that large impact craters or basins are dominant in the polar regions,while small impact craters are dominant in the near equatorial regions.Further research shows that there is a negative correlation between lunar surface fragmentation and density of impact crater on a scale of whole moon.When the minimum number of zones is 36-42,the negative correlation begins to be significant.The spatial distribution pattern of the size of impact craters on the lunar surface is:when centering on the lunar mare areas on the near side of moon such as Mare Imbrium,Oceanus procellarum and Mare Serenitatis and extending outward in turn,the size of impact craters on the lunar surface generally shows a gradual transition from small impact craters to large impact craters.3.The lunar surface fragmentation has a certain spatial differentiation characteristics on the scale of whole moon:the lunar surface fragmentation in the far side of the moon is larger than in the near side,in the polars is larger than in the equator,and in the lunar highland is larger than in the lunar mare.the lunar surface fragmentation is greater in the back than in the front,in the polar regions than in the equatorial regions,and in the land areas than in the sea areas.From the point of view of material composition,the lunar surface fragmentation of multi-component breccia and impact molten rock materials reaches the maximum,mainly concentrated in the two poles of the moon,especially in the Antarctic region;while the lunar surface fragmentation of basaltic lava flows and igneous materials is the minimum,mainly concentrated in the low latitude equator,especially in the southern hemisphere lunar mare area;and the lunar surface fragmentation of impact breccia,local material and volcanic material mixtures is in the middle value,mainly concentrated in the lunar highland near the high latitude Arctic.From the point of view of geological age,the lunar surface fragmentation of the Imbrian Period reached the maximum and its distribution was relatively balanced,while the lunar surface fragmentation of the Copernican Period was the minimum and its distribution was relatively random,and the lunar surface fragmentation in the Periods of Pre-Nectarian,Nectarian and Eratosthenian was in the middle,mainly concentrated in the lunar poles,especially in the Antarctic region.