Morphological characteristics of impact craters with diameters of 5-20 km on the Moon

The morphology of impact craters on the Moon plays an important role in understanding impact cratering process, surface and subsurface properties, and their evolutions. In this study, we systematically analyzed the depth, rim height, slope, and rock abundance of 15,135 impact craters between 5 and 20 km in diameter on the Moon, covering the simple and simple-to-complex transitional crater regimes. We found that the decline rates of inner average slopes of mare craters are generally larger than those of non-maria craters and that the degradation rate of inner upper wall slopes around rim crest is not uniform, which decreases rapidly when the depth/ diameter ratio (d/D) lies in 0.25-0.15 but slowly when d/D is in 0.15-0.05. However, we found that there is no difference in crater rim height between different terrains (e.g., maria and highlands). In addition, we also found the decrease in rock abundance is more rapid than the ejecta infilling of the crater floor, especially for large simple craters. Moreover, we investigated the diameter-dependent morphological features of fresh craters in different terrains and revised the onset of transitional crater diameters based on the 180 freshest craters. We found that crater initial depth depends on target properties (e.g., strength and porosity) whereas that the degradation rate of the crater depth is independent of terrains. Furthermore, we found that the power-law re-lations for depth and diameter of fresh simple craters are d = 0.293D0.865 (mare), d = 0.297D0.884 (highland), d = 0.221D0.959 (north pole) and d = 0.209D0.981 (south pole). The onsets of transitional crater diameters are-14.2 km (mare),-15.7 km (highland),-16.6 km (north pole), and -16.8 km (south pole). These morpho-logical characteristics and their differences in different terrains suggest that target properties (e.g., strength, layering, and porosity) affect the formation and degradation of larger simple and transitional craters.

Automated summary

In this study, the morphology of impact craters on the Moon was analyzed, showing differences in slope, height, and rock abundance between craters in maria and non-maria regions. The findings also revealed differences in degradation rates and depth-dependent features among different terrains. The revised onset of transitional crater diameters was also determined.