The stability of a liquid-water body below the south polar cap of Mars

Radar data from the Mars Express spacecraft show bright subsurface reflections in the Planum Australe area that could be due to liquid water located at a depth of 1.5 km (Orosei et al., 2018). If this interpretation of the data is correct, the presence of such water would have important implications for the present-day thermal state of the region. In this article, we recalculate the depth of the liquid water and we analyze the influence of the regional thermal properties in the surface heat flow and the subsurface temperatures. We have obtained a new depth to the bright reflector between 1.3 and 1.5 km by using a temperature dependent relative permittivity for the water ice and taking into account the dust content in the area. We show that regional properties in the SPLD moderately influence the thermal state of the area where the liquid water is located. A better knowledge of the porosity profile in the studied area is necessary to constrain surface heat flow and subsurface temperatures accurately. Our findings are in agreement with previous work that shows anomalously high local heat flows would be required to sustain liquid water at this location.