High and low frequency electrical measurements of martian soil simulants

The search for gaseous, liquid or ice water in the atmosphere or on/below the surface of the rocky planets and moons of Jupiter and Saturn represents one of the fundamental goals of the interplanetary missions. Spectroscopic methods are best to define the presence of water when studying the surface or atmosphere of a planet, however different methods, such as those developed for geophysical surveys on Earth, are required when exploring the subsurface environment. Some of these techniques are quite precise, such as neutron scattering or NMR, however their application to remote planetary missions is difficult because of high costs, the complexity of their measurements, and their typically large size and weight. In contrast electric and electromagnetic methods are simple, small, very robust and are relatively inexpensive, and thus have great potential for future missions. Our group has proposed the construction, testing and use of electrical and electromagnetic probes within the Mars Surveyor Program (2003-2005) Lander Mission in an effort to measure the electromagnetic parameters of the shallow soil environment on Mars (up to a depth of 50 cm) and, consequently, to determine the presence of H2O liquid, H2O ice or CO2 ice at the landing site. Two different probes have been proposed: a low frequency (IP) probe that works below 10 KHz and which outlines the presence of H2O liquid and ice, and a higher frequency (EM) probe that works above 800 MHz and which is able to define the presence of H2O liquid. Both of the probes can be used either from on surface to investigate a large soil volume, or in a borehole to make point measurements. Given the lack of electrical measurements on the hypothesized Martian materials under the Martian physical conditions, ad hoc experiments were carried out both in the higher and lower frequency ranges. Preliminary results obtained using both dielectric spectroscopy and TDR (Time Domain Reflectometry) methods to measure the dielectric constant of a mixture volcanic sand/H2O (liquid and ice) and volcanic sand/CO2 snow are discussed