AEOLIAN DRIVEN LANDSCAPE EVOLUTION IN THE NOACHIS TERRA AND HELLESPONTUS MONTES REGIONS, MARS

The Noachis Terra (NT) region is well known for hosting numerous dark dune fields. As is commonly observed on Mars, most of these dune fields occur within craters, with the exception of those in Hellespontus Montes (HM) in eastern NT. These locations show many dunes in less typical extra-crater environments with the rugged rim elements of western Hellas. Here we compare these two neighboring dune field populations in the context of their boundary conditions to assess how aeolian-driven landscape evolution may vary spatially. For this task, we utilized HiRISE images (25 cm/pix) for morphology, topography and change detection.

Kilometer-scale surface roughness generally decreases westward with the heavily eroded NT terrain. Sand supply increases west leading to larger dune fields (e.g. Proctor crater on the western edge of the study area). The NT wind regimes, derived from bedform morphology and migration direction, are quite variable with eastward and westward components, whereas a more formative westward wind regime appears to be driving sand transport in HM. Ripple and dune migration rates decrease both westward and southward across the study area. For example, rapidly migrating (>1 m/Earth year) barchan dunes were found along HM, indicating an unconsolidated sand supply driven by anabatic slope winds from Hellas. In contrast, sand ripples in Proctor crater are migrating slowly (~0.3 m/year), while dunes there have not been detected to be advancing in long baseline data (~8 Earth years). Many southern dune fields do not yet show evidence of change or migration in available images. This apparent lack of sand mobility, along with the decreased transport rates, have been attributed to a poleward increase in seasonal volatiles as a stabilization factor. Thus, sediment state likely plays an important role in regional differences. Sediment fluxes and abrasion rates are also greater for HM vs. NT, leading to distinct differences in dune morphology with sharp, steep slipfaces in HM compared to the rounded dune slopes in NT to the west and south. Collectively we attribute the combination of sand supply and topography in HM, along with a key location of the dunes on the edge a major basin, leads to higher sand fluxes relative to most of NT. These higher sand fluxes indicate greater sediment abrasion rates and enhanced landscape evolution along HM.