EMC/ERH-properties of thin layers of martian analogue soils – First results

Abstract

The water content of soils significantly influences their chemical, physical and biological properties. In equilibrium, this water content can be described by the EMC/ERH ratio (EMC – Equilibrium Moisture Content, ERH – Equilibrium Relative Humidity). In view of Mars, the thin layer of the upper millimetres of the martian surface are of particular interest because this soil interacts directly with the diurnally varying atmospheric humidity, which during night and early morning can reach saturation. Adsorption/desorption of water in the soil and freezing of water can be a consequence. A plate capacitor has been developed to determine EMC/ERH ratios for martian thermo-physical conditions. Two martian soil analogue (Bentonite, JSC Mars 1) have been tested. The measurements have been performed in a temperature range from +25°C to -75°C under air and ambient pressure (Earth) with water partial pressure of 0,12Pa.