Effects of thermal conductivity of crust and lithosphere on the temperature Evolution of Mars

Abstract

On Mars, the internal heat is mainly transported by thermal conduction through the outer layers (i.e. lithosphere, crust and regolith). This is due to the lack of plate tectonics since at least the end of the Noachian. Therefore, thermal conduction plays a key role in thermal evolution models. It is based on the thermal conductivity, which is unfortunately poorly constrained for Martian materials. Although it is generally known that the thermal conductivity depends on the structure, composition, temperature and pressure of crust and mantle, difficulties occur in specifying its actual values. Nevertheless, it is possible to find constraints by using lunar and terrestrial analogs and measurements which yield the following values: 0.001 to 2 W/(mK) for the regolith, about 2 W/(mK) for basaltic crust and 2.5 to 3 W/(mK) for mantle material under Martian conditions. Despite these facts previous thermal evolution models assume a constant value of 4 W/(mK) for the crust as well as for the lithosphere and mantle. In our models we investigate the influence of thermal conductivity in crust and lithosphere on parameters like crustal growth or thickness of the elastic lithosphere. In some models we also incorporated a regolith layer, for which we used modified thermal conductivity equations which were originally derived for the lunar regolith. Since the thickness of a layer is also important for its thermal behaviour and estimated crustal thicknesses range from about 10 km at Hellas to about 80 km at Arsia Mons (Montesi and Zuber, 2003), we also studied the effects of lateral crustal thickness variations on the temperature evolution.