Deep-seated gravitational slope deformation scaling on Mars and Earth: same fate for different initial conditions and structural evolutions

Some of the most spectacular instances of deep-seated gravitational slope deformation (DSGSD) are found on Mars in the Valles Marineris region. They provide an excellent opportunity to study DSGSD phenomenology using a scaling approach. The topography of selected DSGSD scarps in Valles Marineris and in the Tatra Mountains is investigated after their likely similar postglacial origin is established. The deformed Martian ridges are larger than the deformed terrestrial ridges by one to two orders, with however a similar height-to-width ratio, ~ 0.24. The measured finite strain of the Valles Marineris ridges is 3 times larger than in the Tatra Mountains, suggesting that starting from two different initial conditions, with steeper slopes in Valles Marineris, the final ridge geometry is now similar. Because DSGSD is expected to be now inactive in both regions, their comparison suggests that whatever the initial ridge morphology, DSGSD proceeds until a mature profile is attained. On both planets, strain is distributed over the same number (~ 5) of major scarps; fault displacements are therefore much larger on Mars. The large offsets make necessary reactivation of the DSGSD fault scarps in Valles Marineris, whereas single seismic events would be enough to generate DSGSD fault scarps in the Tatra Mountains. The required longer activity of the Martian faults may be correlated with a long succession of climate cycles generated by the unstable Mars obliquity. In spite of similar global geometry today, the studied ridges on Mars and Earth affected by DSGSD did not start from similar initial conditions and did not follow the same structural evolution.