Measuring water content of Martian soil simulants using planar four-probes

A miniature four-point probe instrument has been developed and applied to the characterization of the moisture content of the Martian soil simulants using fine and coarse silica sand and Moses Lake basalt. The results indicate that the soil resistivity varies over four orders of magnitude as the moisture content varied from 0.1% to over 10%. In addition it was found that forcing too much current through the sand sample resulted in a curious breakdown in the current-voltage characteristic.