The Formation of Valles Marineris, Mars

Introduction: Valles Marineris is the most prominent tectonic feature on Mars, consisting of troughs up to 2000 km in length, 200 km in width, and 10 km in depth. A scenario for trough formation is here proposed that is consistent with the geological and geophysical evidence, and predicts a priori the observed trough depths. The proposed mechanism entails a combination of Tharsis loading over the crustal dichotomy boundary, a narrow band flexural tensile stresses along the buried boundary, magmatic weakening of the lithosphere, vertical subsidence of super-isostatic crust, and sedimentary loading. The mechanism is outlined below in a series of sequential stages. Stage 1: Impact origin for the martian dichotomy. The first event of direct relevance to the formation of Valles Marineris is the origin of the martian dichotomy. Recent work supports an impact origin for the dichotomy on the basis of the elliptical shape of the northern lowlands, in resemblance to other giant impact basins [1]. Regardless of the mechanism, the formation of the crustal dichotomy resulted in a step function in topography and crustal thickness across a boundary that nearly bisects Tharsis (Figure 1). Significantly, Valles Marineris is south of and semiparallel to the buried boundary.