THE RELATIONSHIP BETWEEN SURFACE ROUGHNESS AND SURFACE AGE ON MERCURY

Surface roughness is the quantitative measure of change in vertical topography over a given horizontal scale. Past studies of surface roughness on the Moon and Mercury have noted a correlation between higher surface roughness values and geologic units with higher crater density and it has been proposed that the age of a surface can be estimated by measuring the surface roughness. This would provide another measure of the age of surfaces from remote sensing. Modeling studies have focused on the topography of an idealized crater shape to try and understand the relationship between surface age and surface roughness.

In this study, we investigate the relationship between surface age and surface roughness through simulation. We make use of observed surface roughness around one crater at a given scale, and then co-add those results other observed roughness measurements of roughness seen at craters of other scales. In this way, we can simulate how the measured roughness on Mercury evolves as crater density increases with the increasing passage of time. We limit our simulations to the observed surface roughness measured around craters with diameters ranging from 10 to 100 km.

Preliminary results show that for surface roughness at the 1 km scale, the total number of craters in a region does not control the surface roughness, but instead the surface roughness is dominated by the formation and presence of a few large impact craters. This is supported by our observations that a few large impact craters dominate the surface roughness at the 1 km baseline in the volcanic plains of Mercury. For Mercury, the relationship between surface roughness and surface is not directly related and instead the more complex topography around large craters obscures any affect crater density has on surface age