Polar wandering history of Mars: triggered by giant impact and mantle super-plume?

Polar wander is not an unusual phenomenon for many terrestrial planets, but the history, processes and triggers are complexity and little is well understood. Mars may be the best planets for studying this process, because most geological history was well preserved. Much evidence indicates that the present spin axis of Mars is not the same as that in its ancient and recent time. Many authors have discussed the polar wander history based on magnetic anomalies (e.g. Arkani-Hamed, 2001; Hood and Zacharian, 2001; Hood et al., 2005; Arkani-Hamed and Boutin, 2004; Boutin and Arkani-Hamed, 2006), topography and sediments (Murray and Malin, 1973; ) , geoid (Sprenke et al., 2005), and giant impact basins (Schultz and Lutz-Garihan, 1982; Arkani-Hamed, 2009) respectively. These studies suggest that the martian spin axis has wandered about 10o-20o in the past 100myr (Murray and Malin, 1973), 15-90o polar motion in the past 4.2Ga due to load of Tharsis bulge (Sprenke et al., 2005), and a combined model suggests forming of Alba Patera and Elysium Rise caused spin axis rotating counterclockwise to equator and subsequent volcanism and giant impacts deduced mass concentrations caused further clockwise rotation to its present position during 4.2-3.9Ga. However, most of these hypotheses are model-dependent and have not well correlated to geological records, especially unique polar deposits and geomorphology. There are many unanswered questions about paleopole deposits, paleo-magnetic poles locations, polar wander, true polar wander, obliquity, and their relation with external and internal force driven events, such as giant impact, mantle plume and it caused volcanic mass loading. By examining possible ancient polar deposits, combining with giant impact history, orientation of magnetic field and compared with previously suggested polar wander models, this study proposed a comprehensive hypothesis that could explain major polar wander events and suggest that giant impacts and volcanism could be major triggers, although polar wander could be a more complex processes and have many other causes.