Potentials of low frequency sounding radar for water exploration in the Martien subsurface

The performances of low frequency sounding radars are strongly related to the ability of the electromagnetic waves to penetrate the geological materials constituting the studied soil. The aim of our research is to study experimentally the geo-electrical and geo-magnetic properties of the Martian sub-surface and simulate the backscattered radar echo in the frequency band 1-20 MHz, in order to determine the ability of future radar sounding experiments to detect the possible presence of water in the Martian sub-surface, few hundreds of meter deep. In the first part, we constructed experimentally a most common dielectric profile representative of the Martian sub-surface starting from the general geological description of the Martian sub-surface by measuring the electric permittivity and magnetic permeability of well-defined volcanic and sedimentary materials that have been reported for Mars. This led to synthetic representative samples of the Martian sub-surface materials under adequate conditions of porosity and temperature that should exist in the first 2.5 km of the upper crust. This 2 MHz geo-electrical profile was used to evaluate the penetration depth and losses of the radar signal. In the second part, we constructed four geological models corresponding to terrains where we considered the possibility of finding liquid water lenses at shallow depths. Those localities could be considered as potential landing sites of the Netlander GPR experiment. We conducted series of measurements of the electromagnetic properties of local volcanic and sedimentary materials that might be present on those sites. This led to the construction of four realistic geo-electrical models. We finally used the FDTD technique to simulate the radar backscattered echo for each site considering the Netlander GPR parameters.