Quantitative Characterization of Impact Crater Materials on the Moon: Changes in Topographic Roughness and Thermophysical Properties With Age

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Abstract
Impact craters are the dominant features on the Moon, and their degradation with time is the most common geological process on this body. This work is aimed at detailed quantitative characterization of this process. We quantitatively characterize crater materials by (1) the topographic roughness calculated from Lunar Orbiter Laser Altimeter and (2) rock abundances and nighttime soil temperatures derived from Diviner measurements. In contrast to preceding works, we separately consider crater material subunits: central peaks, floors, walls, and continuous ejecta to study their degradation in detail. We mapped totally 4,770 individual crater material subunits. All subunits of the youngest craters are characterized by increased roughness, rock abundance, and soil temperature. These parameters decrease with age and tend toward equilibrium, stable state; the continuous ejecta reach equilibrium more rapidly than other subunits. Kilometer‐baseline roughness of crater walls in the lunar maria is higher than in the highlands. Rock abundances and soil temperatures of the walls and floors of simple craters in the maria are also higher than in the highlands. We attribute these trends to differences in the mechanical properties of the target materials. Although the properties studied are not exact proxies for age, they can be used to assess individual age predictions; for example, several craters that were erroneously classified as Copernican have been detected. We also found that the unusual thermophysical signature of the walls of the Late Imbrian crater Bonpland D is due to recent regolith flows that could have been caused by a strong, shallow seismic event.
Funding Information
  • Russian Foundation for Basic Research (16‐37‐00323)
  • National Aeronautics and Space Administration (NNX16AQ06G)
  • National Natural Science Foundation of China (41490634, 41773065, 41941003)

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