RELATIONSHIP BETWEEN PROMINENT TECTONIC FEATURES AND GLOBAL ELEVATION ON MERCURY

We analyze elevation on Mercury at the locations of prominent tectonic features (>50 km in length), in order to test the hypothesis that the formation and/or development of these contractional landforms contributed to the long wavelength topography. Global contraction explains the formation of widespread thrust faults (lobate scarps and high-relief ridges), but by itself would result in a random pattern of faults. Prominent fault scarps have average orientations that change with latitude, are concentrated in a few longitudinal bands, and are twice as numerous in the southern hemisphere than in the north.

Prominent scarps were mapped from high-incidence angle images (resolution of 0.2–0.3 km/pixel) from the Mercury Dual Imaging System (MDIS) on MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER). A global digital elevation model (DEM; 2.0–3.0 km/pixel, vertical uncertainty of 0.3 km) made from photogrammetric control points, which included a solution for radius, was used to produce the global monochrome mosaic; elevation has a symmetric, unimodal distribution. Mercury has a dynamic range in elevation of 10.5 km, less than that of Mars or the Moon.

Preliminary results show that lobate scarps occur in elevations ranging from -2.9 to 3.5 km (mean of 0.0 km, standard deviation of 0.8 km). The distribution of elevations where scarps are found is very similar to that of the global DEM, with the same mean but a smaller overall range (scarps are found in all elevation bins with >1% areal coverage). The similarity in means, ranges, and distributions of elevations indicates that prominent lobate scarps are not correlated with any particular elevation range and thus do not significantly contribute to regional-scale topography (high or low). This suggests that much of the long wavelength topography on Mercury was shaped by processes not directly linked to those that localized prominent thrust faults, including impact processes, volcanism, and (possibly) mantle induced dynamic topography.