On the current thermal state of Mars

Abstract

<p>The current thermal state of Mars is a fundamental unknown in Mars science. Although is has a huge influence on the planet’s current geodynamic activity and controls the possibility for basal melting at the polar caps [1], constraints on this quantities are very scarce. This situation has lately been improved by the study of lithospheric deformation at the north polar cap [2] which constrained the current Martian elastic lithosphere thickness T_e, an indirect measure of the temperatures in the planetary interior.</p><p> Using radar sounding data obtained bySHARAD, the shallow radar onboard the Mars Reconnaissance Orbiter, [2] found that the current Martian lithosphere is extremely stiff and T_e is larger than 300 km today. This is surprising as this value is almost twice as large as previously estimated from theoretical considerations and flexure studies [3][1].</p><p> In order to be consistent with the planets thermal evolution, [2] argue that the amount of radioactive elements in the Martian interior needs to be subchondritic. This appears to be problematic as geochemical analysis of the SNC meteorites implies higher concentrations of radioactive elements [4]. Furthermore, if the concentration of heat producing elements is indeed reduced, the resulting low interior temperatures will inhibit partial mantle melting and magmatism. However, geological evidence suggests that Mars has been volcanically active in the recent past [5]. In order to address these inconsistencies, we reinvestigate the thermal evolution of Mars and examine its current thermal state for a wide range of initial condition using the current elastic thickness T_e and the potential for partial mantle melting to constrain our models.</p> [1] M.A.Wieczorek, Icarus, 10.1016/ j.icarus. 2007.10.026 (2008).<br /> [2] R.J. Phillips et al., Science 320, 5880, 1182 (2008) <br /> [3] M. Grott, D. Breuer, Icarus 193, 503 (2008). <br /> [4] H. W¨anke and G. Dreibus, Philos. Trans. R. Soc. London Ser. A 349, 285 (1994).<br /> [5] G. Neukum et al., Nature 432, 971 (2004).<br />