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Characterization of the Density Dependent Dielectric Properties of Mars-like Soils: Implications for Mars Radar Studies

Introduction: Mars is the subject of several present and future radar investigations over the frequency range 1 MHz to 1GHz investigating the physical properties of the Martian surface and subsurface. A primary objective of the ESA orbital sounding radars, MARSIS (0.5-5 MHz) and SHARAD (15-25 MHz) is to map the Martian subsurface looking for evidence of subsurface water. The scientific return from these radar instruments is dependent on the understanding of the electromagnetic characteristics of the areas under investigation, which determine the reflection, transmission and attenuation of radar signals. In the absence of significant amounts of magnetic materials, the amount of attenuation expected will depend on the dielectric properties. At radar frequencies the dielectric permittivity of surface dry rocks and sediments will be sensitive to a variety of parameters but is dominantly controlled by frequency, the soil’s densities and mineralogical content [1,2]. Previous dielectric measurements [3,4] and radar field studies in Martian analog environments [5] show that the first surface layers can cause significant attenuation of radar waves, especially if iron oxide minerals are present in Mars-like amounts. It is therefore essential to acquire an adequate knowledge of the dielectric properties of Mars-like soils as a function of the surface geophysical conditions. This investigation presents laboratory measurements of the complex dielectric permittivity of a variety of synthesized and Mars analog soils with varying iron oxide content, over the frequency range 1 MHz-1 GHz and density range 0.8-2.4 gcm (covering the density range of the Martian surface dust as deduced from TES thermal inertial data).