The Surface Roughness of Large Craters on Mercury

摘要

abstract_textpThis study investigates how individual large craters on Mercury (diameters of 25-200 km) can produce surface roughness over a range of baselines (the spatial horizontal scale) from 0.5 to 250 km. Surface roughness is a statistical measure of change in surface height over a baseline usually after topography has been detrended. We use root mean square deviation as our measure of surface roughness. Observations of large craters on Mercury at baselines of 0.5-10 km found higher surface roughness values at the central uplifts, rims, and exteriors of craters, while the crater floors exhibit the lowest roughness values. At baselines 10 km, the regions exterior to large craters with diameters 80 km have the highest surface roughness values. These regions, which include the ejecta and secondary fields, are the main contributors to the increased surface roughness observed in high-crater density regions. For baselines larger than 10 km, the crater cavity itself is the main contributor to surface roughness. We used a suite of numerical models, utilizing the measured surface roughness obtained in the study, to model the cumulative effect of adding large craters to a surface. The results indicate that not all of the surface roughness on Mercury is due to fresh large craters but that impact craters likely contribute to the Hurst exponent from baselines of 0.5-1.5 km and the shape of the deviogram. The simulations show that the surface roughness varied around an asymptote at the baselines studied before the surface was covered in impact craters./ppPlain Language Summary Impact cratering is the main process by which many planetary bodies are roughened, where an increase in the number of craters is related to higher surface roughness. In this study, we use observations and artificial data to explore how individual complex craters on Mercury can change the surface topography and produce surface roughness. Observations of the surface roughness of complex craters on Mercury found surface roughness related to several different geologic features of the craters. We found that impact craters are the main source of surface roughness on Mercury. We modeled how impact crater density affects surface roughness and found that it is difficult to relate surface age to surface roughness./p/abstract_text