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

Abstract

A line-heat source apparatus was used to measure thermal conductivities of a lightly cemented fluvial sediment (salinity = 1.1 g • kg -1), 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 3x 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 μm in diameter, with 60% of the sample being less than 63 μm in diameter. As much as 35% of the cemented sample was composed of conglomerate particles with diameters greater than 500 μm. The thermal conductivities of the cemented sample were most similar to those of 500-μm glass beads, whereas the thermal conductivities of the uncemented sample were most similar to those of 75-μm 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. Copyright 2009 by the American Geophysical Union.