Polar Wander of Mars Driven by Degree-1 Mantle Convection and Its Implications for the Formation of the Crustal Dichotomy and the Tharsis Rise

The topography on Mars is dominated by the crustal dichotomy between the northern and southern hemispheres and the Tharsis rise on the equator[1]. No explanation has been offered so far as to why the dichotomy should be in its current orientation rather than another. The geoid is currently dominated by Tharsis [2] and rotational stability suggests that a Tharsis-sized load would induce polar wander to place itself on the equator if it did not originate there [3]. However, little tectonic evidence for this excursion exists [4]. Furthermore, it is possible to place Tharsis on the equator and allow the dichotomy to have an arbitrary orientation. Here, we examine mechanisms that may be responsible for the formation of the crustal dichotomy and its current orientation. It has been shown that degree-1 mantle convection can arise in early Mars-like conditions on a timescale (within the first couple hundred Ma) appropriate to the formation of the dichotomy [5]. Geoid anomalies arising from mass heterogeneities due to convection and from the resulting dynamic topography may induce polar wander and reorient the planet.