Electrical-impedance measurements serve as sensitive indications of moisture content.

An apparatus has been developed for measuring the low concentrations of liquid water and ice in relatively dry soil samples. Designed as a prototype of instruments for measuring the liquid-water and ice contents of Lunar and Martian soils, the apparatus could also be applied similarly to terrestrial desert soils and sands. The high sensitivity of this apparatus is best appreciated via a comparison: Whereas soil moisture contents of agricultural interest range between 3 and 30 weight percent, this apparatus is capable of measuring moisture contents from 0.01 to 10 weight percent (at room temperature). Moreover, it has been estimated that optimization of the design of the apparatus could enable measurement of moisture contents as low as 1 part per million by weight.