Remote temperature measurements have increased our understanding of the physical properties of the Martian surface layer. Typical grain sizes, rock abundances, subsurface layering, soil cementation, bedrock exposures, and ice presence/compositions have been derived and mapped using temperature data in conjunction with subsurface models of heat conduction, and have helped to constrain numerous global-scale processes. However, the simplicity of these models precludes more significant advances in the characterization of the physical nature of the Martian surface. For this seminar, I will present a new model of heat conduction for planetary soils derived from a combination of finite element modeling and laboratory measurements for homogeneous particulated media accounting for the grain size, porosity, gas pressure and composition, temperature, and the effect of any cementing phase. I will show that incorporating the temperature dependence of bulk conductivity alters the predicted diurnal and seasonal temperatures as compared to temperatures predicted with a temperature-independent conductivity model. Inconsistencies between observed temperatures and those predicted using temperature-independent conductivity models have been interpreted to result from subsurface heterogeneities, but they may partially be explained by a temperature-dependency of the thermal inertia, with additional implications on the derived grain sizes. Cements are shown to significantly increase the bulk conductivity of a particulated medium, and bond fractions <5% per volume are consistent with Martian thermal inertia observations previously hypothesized to correspond to a global duricrust. I will conclude with general thoughts on the predicted thermophysical properties of particulated materials on other planetary bodies with atmospheres.
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Institute for Planets and Exoplanets
