Surface Roughness of the Chang’E-6 Lunar Samples and Landing Site from Submicrometer to Kilometer Scales: Implications for Lunar Surface Processes and Remote Sensing Data Modeling

Although lunar surface roughness was studied extensively above micrometer scales before, it has not been investigated at smaller scales. In this study, we used an atomic force microscope to measure surface elevations of the Chang’E-6 lunar samples at submicrometer scales and collected other topographic data of the Chang’E-6 landing site at larger scales, which allowed us to calculate lunar surface roughness parameters across unprecedented 11 orders of magnitude from submicrometers to kilometers. The goal of this study is to investigate how surface roughness is linked to geological processes on the Moon and influences lunar remote sensing observations. The rms deviation increases with spatial scale and exhibits a scale-dependent behavior characterized by the Hurst exponent. The Hurst exponent peaks at 42 m, where impact cratering dominates, and exhibits the lowest value at 4 mm where rock fragmentation and regolith formation prevail. The Hapke’s mean slopes revealed that the lunar photometric response is sensitive to roughness scales of 100 μ m. The rms slopes showed that the lunar thermal infrared (TIR) data are sensitive to roughness scales of 100 μ m to 5 cm, and the rms heights indicated that the absorption band depth measured for an individual particle in the TIR wavelengths may change by 17% when considering micrometer-scale roughness. The rms height and autocorrelation length suggested that the Chang’E-6 landing site is radar rough at a wavelength of 12.6 cm, and that the radar echoes can be modeled by the Kirchhoff Approximation or the Improved Integral Equation Model.