Water detection in the Martian subsurface

Performances of low frequency sounding radars, in term of penetration depth and signal to noise ratio, are mainly function of electric and magnetic losses, volume scattering, and interface roughness. In order to evaluate experimentally the impact of each of those parameters on the future sounding radar missions foreseen for Mars exploration, we conducted series of measurements of the electromagnetic properties of volcanic and sedimentary materials that may be present in the near Martian subsurface layers. Results were used to construct some representatives geoelectrical profiles of the Martian subsurface for the 1-20 MHz frequency range. We considered in particular a simple 3- layered model, which is a primary model to describe terrains where recently observed fluvial-like features raise the possibility that liquid water may exist at shallow depths (100 to 500 meters). We used expected subsurface geophysical conditions such as temperature gradient, rock porosity that may exist for such sites (Clifford, 1993) to construct representative laboratory samples for each layer. We integrated the measured EM characteristics in a geoelectrical model including interface roughness and volume scatterers. We then used the Finite Difference Time Domain (FDTD) algorithm to simulate the radar backscattered echo and evaluate the ability of future sounders to detect the probable presence of ground ice — wateri nterfacei n such a geological configuration.