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

Abstract

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 (≥ 100 m in diameter) per 100 km2; 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.

The Provenance of Regolith at the Chang'e‐5 Candidate Landing Region

“…Based on the TiO 2 and FeO contents, and a false color composite map from the Kaguya Multiband Imager data, eight geological units were recognized inside the Chang'e-5 candidate landing region (Wu et al, 2018). The absolute model ages (AMAs) of these units were estimated based on crater size-frequency distributions ( Figure 1a and Table 2; Wu et al, 2018), which are consistent with the results of Zhao et al (2017) and Qian et al (2018). Volcanic activity on the Rümker plateau formed the three Late Imbrian-aged basaltic units IR1, IR2, and IR3 (Zhao et al, 2017) at approximately 3.57, 3.58, and 3.62 Ga, respectively (Wu et al, 2018).…”

“…The absolute model ages (AMAs) of these units were estimated based on crater size-frequency distributions ( Figure 1a and Table 2; Wu et al, 2018), which are consistent with the results of Zhao et al (2017) and Qian et al (2018). Volcanic activity on the Rümker plateau formed the three Late Imbrian-aged basaltic units IR1, IR2, and IR3 (Zhao et al, 2017) at approximately 3.57, 3.58, and 3.62 Ga, respectively (Wu et al, 2018). Two Late Imbrian-aged mare surfaces were formed during a later major phase of basaltic volcanism in this region (Qian et al, 2018), that is, units Im1 (~3.48 Ga) and Im2 (3.47 Ga) shown in Figure 1a (Wu et al, 2018).…”

“…The candidate landing region for Chang'e-5 is near the Mons Rümker volcanic complex in the northern Oceanus Procellarum (Zeng et al, 2017;Zhao et al, 2017). It covers an area of 10°× 3°(53-63°W, 41-44°N), as shown in Figure 1a (Wu et al, 2018). Chang'e-5 will be the first sample return mission since the Luna 24 mission that was carried out in 1976.…”

“…Distantly sourced particles (DSPs) delivered via ballistic transportation of ejecta from distal impact craters are important components of lunar regolith (Huang et al, 2017), which is evident by the ubiquitous occurrence of impact rays on the Moon. When impact ejecta land on the target surface, local materials are excavated by and mixed with the ejecta by a process called ballistic (Wu et al, 2018). The green stars denote the geographic center of the eight geological units.…”

Analysis of Rock Abundance on Lunar Surface From Orbital and Descent Images Using Automatic Rock Detection

“…We used images from different sources for rock detection and rock abundance analysis, including (1) georeferenced descent images (0.02–0.17 m/pixel) around the Chang'E‐3 landing area (19.51°W, 44.12°N; Wu et al, ), (2) high‐resolution LRO NAC images (0.3–1.1 m/pixel) covering the landing sites of the Chang'E‐3, Luna 17 (35°W, 38.24°W), and Luna 23 (62.15°E, 12.67°N), and (3) LRO NAC image mosaic with a relatively low resolution (1.5 m/pixel) and covering an area of 182 × 166 km 2 (55–49°W, 41–45°N) in the Oceanus Procellarum, which belongs to a part of the candidate landing area of Chang'E‐5 (Wu et al, ).…”