Meter‐Scale Topographic Roughness of the Moon: The Effect of Small Impact Craters

Abstract

High‐resolution digital terrain models (DTMs) generated from the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Cameras (NACs) provide an opportunity to study surface roughness of the Moon at meter scale. In this study, we mapped and investigated meter‐scale topographic roughness over 462 regions of the Moon using NAC DTMs. Our results show that, at meter to hectometer scales, there are obvious differences in median bidirectional slope, root‐mean‐square (RMS) height, and median absolute slope between maria and highlands. In terms of the median value, ratios of the bidirectional slope, RMS height, and median absolute slope within the maria and highlands are 1: 2.4, 1: 3.0, and 1: 2.7, respectively. However, up to a baseline of ∼0.2 km, no discernible differences in the Hurst exponent and median differential slope exist between the maria and highlands. The Hurst exponent varies from 0.7 to 0.95, with a median value of 0.9 within both the maria and highlands. To identify potential factors affecting meter‐scale roughness of the Moon, we compared the maria with volcanic features on Earth and Mars, as well as the lunar highlands with simulated cratered terrains. We found that the Hurst exponents within the lunar maria are much larger than those of the volcanic features on Earth and Mars, mainly because the lunar maria accumulated more impact craters with diameters smaller than 1 km. The Hurst exponents within the highlands are consistent with those of the simulated cratered terrains, whose surface roughness depends primarily on crater shape, number density, and stratigraphic age. All these results indicate that lunar surface roughness at meter to hectometer scales is mainly controlled by small degraded impact craters.

Regolith Properties in the Chang'E‐5 Landing Region of the Moon: Results From Multi‐Source Remote Sensing Observations

“…Examination in the optical image (Figure 7a) shows that there are degraded craters with diameter of ∼70–200 m. According to their morphologic prominence, they can be classified as moderately degraded craters of morphologic type B, with a typical depth/diameter ratio of 0.1. A recent study shows that depth/diameter ratio of small fresh craters at this large is ∼0.13–0.16 (Cai & Fa, 2020). If the difference in crater depth between fresh and degraded craters is regarded as regolith thickness, then the thickness of regolith can be estimated as 2–12 m. Therefore, our estimation of ∼1.5 m to >8 m regolith thickness at the CE‐5 landing region is reasonable.…”

Self-Organization Characteristics of Lunar Regolith Inferred by Yutu-2 Lunar Penetrating Radar

“…The weak heterogeneity of the lunar regolith does not seriously influence the imaging and inversion [24,29,30] because it is too weak compared with the reflections from the ejecta. However, further study of these weak heterogeneous characteristics would be helpful in revealing the process of lunar regolith formation, particularly to the most recent stage of local small impacts [31]. Of course, long-distance heavy bombardments may also convey an amount of small-particle ejecta and contribute to such an ultra-thick layer of fine regolith on the far side of the Moon [32].…”

Reunderstanding Geomorphological Features in Chang'e-5 Sampling Region Based on Multiscale Roughness Model

“…For hectometer-scale roughness analysis, Kreslavsky et al [13] considered that no significant roughness differences existed between maria and highlands. Cai and Fa [14] showed that hectometer-scale roughness textures were mainly controlled by small and degraded impact craters. The proposed roughness maps indicate that more complex geomorphological features cause the higher roughness textural changes.…”

“…Generally, the multi-scale roughness properties of lunar surface are discussed at meter-scales, hectometer-scales, and kilometer-scales. The meter-scale roughness parameters of the lunar surface are mainly controlled by small and degraded impact craters [14]. Hectometer-scale roughness is related to the regolith accumulation and modification processes, while kilometer-scale roughness reflects major geological events [13].…”

“…Kreslavsky et al [13] indicated that roughness map was a useful tool to save the time and provide convenient textures for visual interpretation. Slope-based roughness method is one of the most popular method for lunar terrain analysis [14,15]. However, the calculated roughness textures cannot show obvious topographic signatures to show the differences of each geologic unit [Fig.…”