Outflow activity near Hadriaca Patera, Mars: Fluid‐tectonic interaction investigated with High Resolution Stereo Camera stereo data and finite element modeling

摘要

We investigate the formation of the outflow channels Dao and Niger Valles near the eastern rim of the Hellas impact basin, Mars. Methods used include image and topography analysis, surface age determination, and finite element modeling. Observations show that deep depressions, source regions for Dao and Niger Valles, are located in an area of shallow subsidence to the south and east of the volcano Hadriaca Patera. Cratering model ages allow for fluvial processes triggered by volcanic loading. Based on the observations, we develop a numerical model of volcanic loading on top of a poroelastic plate leading to flexure and fracturing of the lithosphere. Modeling results show that fracturing may occur up to a depth of about 6 km within an area of shallow subsidence, i.e., the moat surrounding the volcano. Depending on initial aquifer pressurization, groundwater could have reached the surface. Model discharges and channel morphometry suggest that the Dao Vallis channel never reached bankfull flow and that the wetted channel perimeter may have formed during multiple outflow events. The following scenario is proposed: (1) emplacement of a volcanic load on top of a confined, overpressurized aquifer in the early Hesperian, (2) fracturing around the load, possibly reactivated during various stages of volcanic activity, (3) channeling of groundwater to the surface along fractures and outflow channel formation during several events in the Hesperian, and (4) collapse, mass wasting and modification of depressions in the Amazonian.