The Surface Roughness of Large Craters on Mercury

Abstract

This 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.

Examining the Potential Contribution of the Hokusai Impact to Water Ice on Mercury

“…The continuous ejecta deposit is approximately symmetric about the crater and lies within one crater radius of the rim. Surface roughness around this crater has a different pattern with radial distance from those observed around other large, fresh craters on Mercury (Susorney et al, ). This difference is associated with the ropey properties of Hokusai's near‐rim ejecta, and a less pronounced secondary ejecta field, relative to similar‐sized craters Abedin and Stieglitz, which, like Hokusai, lie within the northern smooth plains.…”

Surface Roughness and Gravitational Slope Distributions of Vesta and Ceres

“…Large lunar craters are often surrounded by rings of smoother proximal ejecta, while distal ejecta becomes rougher with increasing distance from the crater (Kreslavsky et al, ). Roughness signature of large fresh craters on Mercury is similar to that on the Moon, with some smoother rings in the proximal part of continuous ejecta (Kreslavsky et al, ; Susorney et al, ). Fresh craters are also rough on Mars (Kreslavsky & Head, ), where smooth rings are observed only in a few cases, while typical Martian double‐layer and multilayer continuous ejecta have a high short‐baseline roughness.…”

Surface Roughness Variation Across Polar Ice Deposit Boundaries on Mercury

“…Finally, Susorney et al. (2017, 2018) mapped RMS deviation (45–90°N, 0.5–250 km) to study the effects of cratering, volcanism, and tectonism on surface roughness.…”

“…Kreslavsky et al (2014) also demonstrated this comparison by mapping the interquartile range of topographic profile curvature (65-85°N, baselines 0.7-11 km) and used their roughness calculations to suggest regolith on Mercury is thicker than lunar regolith. Finally, Susorney et al (2017Susorney et al ( , 2018 mapped RMS deviation (45-90°N, 0.5-250 km) to study the effects of cratering, volcanism, and tectonism on surface roughness.…”