Spectral Analysis of the Morphology of Fresh Lunar Craters II: Two‐Dimensional Surface Elevations of the Continuous Ejecta, Wall, and Floor

The morphology of fresh lunar craters provides important clues about how craters of different sizes form, and is used as a baseline for understanding how craters evolve over time. Topographic spectral analysis is a powerful tool for studying the morphology of lunar craters, as it can quantify the scale‐dependent topographic variation of individual crater morphologic features. Furthermore, the 2D topographic power spectrum can reveal the spatial directionality of surface features, as an object with a preferred orientation in the space domain will exhibit a pattern rotated by 90 in the wavenumber domain. In this study, we calculate the 2D power spectral densities of surface elevations of three morphologic features of fresh lunar craters, including the continuous ejecta, wall, and floor, from a subset of 104 Copernican‐ and Eratosthenian‐aged craters larger than 1 km in diameter. The calculated power spectral density in general decreases with increasing wavenumber, indicating that the crater surface is smoother at smaller scales. We fit the obtained 2D power spectral density using a function with four parameters that characterize important topographic properties of fresh lunar craters, including how topographic variation is distributed across length scales and how the relative strength of radial or circumferential topography changes in different morphologic features. We derive the dependence on crater diameter for each of the four fit parameters for each morphologic feature, and then use the empirical fits to generate a 3D shape model for synthetic fresh lunar craters, which can be used as input when modeling lunar landscape evolution.