Rock Abundance and Crater Density in the Candidate Chang'E-5 Landing Region on the Moon

Chang'E-5 is China's first lunar sample-return mission, which will be launched in 2019. Understanding the distribution of rocks and craters in the candidate landing region is important for selecting suitable landing sites and studying the surface geology. This paper first separately investigates rock abundance and crater density in the candidate landing region, then provides a joint analysis of them, for the purposes of identifying potential hazards for safe landing and their geological implications. The results indicate that in the region, rocks are mostly concentrated around rocky ejecta craters. About 90% of the region has a rock abundance (the fractional area covered by rocks) of less than 1%. The average crater density is about 250 craters ( 100m in diameter) per 100km(2); on average, 13.5% of the region is covered by craters. The surface ages of geologic units in the region estimated using crater size-frequency distribution indicate that the eastern part of the region is younger than the western part. The joint analysis of rock abundance and crater density identifies local areas that are relatively unfavorable for safe landing. The joint analysis also indicates an exponential relationship between overall rock abundance and crater density, and a roughly linear relationship between overall rock abundance and surface age. Furthermore, the joint analysis indicates an inverse correlation between rock abundance and the relative maturation of craters. The presented research and results will be helpful for identifying suitable landing sites for the Chang'E-5 lander. They also provide fresh insights into lunar surface geology. Plain Language Summary Chang'E-5 is China's first lunar sample-return mission, which will be launched in 2019. Understanding the distribution of rocks and craters in the candidate landing region is important for selecting suitable landing sites and studying the surface geology. This paper first separately investigates rock and crater distributions in the candidate landing region, then provides a joint analysis of them, to identify potential hazards for safe landing and their geological implications. The results indicate that in the region, rocks are mostly concentrated around rocky ejecta craters. About 90% of the region are almost rock free. There are about 250 craters ( 100m in diameter) per 100km(2). The surface ages of units in the region estimated from the crater distributions indicate that the eastern part of the region is younger than the western part. The joint analysis of rock and crater distributions identifies local areas that are relatively unfavorable for safe landing. The joint analysis also indicates relationships among the rock distribution, crater distribution, maturation of craters, and surface ages. The presented research and results will be helpful for identifying suitable landing sites for the Chang'E-5 lander. They also provide fresh insights into lunar surface geology.