The effect of salt crust on the thermal conductivity of one sample of fluvial particulate materials under Martian atmospheric pressures

[1] A line-heat source apparatus was used to measure thermal conductivities of a lightly cemented fluvial sediment (salinity = 1.1 g kg ), and the same sample with the cement bonds almost completely disrupted, under low pressure, carbon dioxide atmospheres. The thermal conductivities of the cemented sample were approximately 3 higher, over the range of atmospheric pressures tested, than the thermal conductivities of the same sample after the cement bonds were broken. A thermal conductivity-derived particle size was determined for each sample by comparing these thermal conductivity measurements to previous data that demonstrated the dependence of thermal conductivity on particle size. Actual particle-size distributions were determined via physical separation through brass sieves. When uncemented, 87% of the particles were less than 125 mm in diameter, with 60% of the sample being less than 63 mm in diameter. As much as 35% of the cemented sample was composed of conglomerate particles with diameters greater than 500 mm. The thermal conductivities of the cemented sample were most similar to those of 500-mm glass beads, whereas the thermal conductivities of the uncemented sample were most similar to those of 75-mm glass beads. This study demonstrates that even a small amount of salt cement can significantly increase the thermal conductivity of particulate materials, as predicted by thermal modeling estimates by previous investigators.