The early heat loss evolution of Mars and their implications for internal and environmental history

Abstract

The time around 3.7 Ga ago was an epoch when substantial changes in Mars occurred: a substantial decline in aqueous erosion/degradation of landscape features; a change from abundant phyllosilicate formation to abundant acidic and evaporitic mineralogy; a change from olivine-rich volcanism to olivine-pyroxene volcanism; and maybe the cessation of the martian dynamo. Here I show that Mars also experienced profound changes in its internal dynamics in the same approximate time, including a reduction of heat flow and a drastic increasing of lithosphere strength. The reduction of heat flow indicates a limited cooling (or even a heating-up) of the deep interior for post-3.7 Ga times. The drastic increasing of lithosphere strength indicates a cold lithosphere above the inefficiently cooled (or even heated) interior. All those changes experienced by Mars were most probably linked and suggest the existence of profound interrelations between interior dynamics and environmental evolution of this planet.

Present-day heat flow model of Mars

“…For Mars, if we take into account a present-day radioactive heat production equivalent to a surface heat flow of 14.3 mW m −2 , according to the compositional model of Wänke and Dreibus37, and the average surface heat loss deduced from our model (19 mW m −2 ), then an Urey ratio of around 0.75 is obtained for the present-day Mars. This value is higher than the Ur (0.594 ± 0.024) proposed from some recent thermal evolution models38, but consistent with a more limited cooling deduced from lithospheric strength analysis1.…”

“…Thus, Ur constitutes an excellent means to visualize the present-day internal heat budget of the red planet, because it describes possible interior cooling or warming. Therefore, if we compared the available information on the Urey ratio throughout the history of Mars, we should be able to constraint more accurately its thermal history1.…”

Sources of water for the outflow channels on Mars: Implications of the Late Noachian “icy highlands” model for melting and groundwater recharge on the Tharsis rise

“…Jellinek et al (2008) estimated the heat flux within the Tharsis region during the time of uplift to be $ 60-100 mW/m 2 based upon mantle convection modeling, and topographic and magnetic field observations. This prediction is in general agreement with paleo-heat flow estimates from (1) lithospheric strength measurements, suggesting that the heat flow in the Tharsis region during the Noachian was $50 mW/m 2 (Ruiz et al, 2011(Ruiz et al, , 2014, and (2) heat transfer modeling performed by Fassett and Head (2006) indicating that the broad heat flux across an edifice with an intruding magma reservoir is $50-100 mW/m 2 .…”

Lithospheric structure of Venus from gravity and topography

“…However, this might be true only taking into account the relatively young ages typical of the venusian surface (e.g., Basilevsky and Head, 1998;Guest and Stofan, 1999;Ivanov and Head, 2011), because a very high range of T e values could be indicating a temporal trend. Indeed, the range of T e values obtained for Mars (for a compilation see Ruiz, 2014) is larger than for Venus, but it seems mostly to be a consequence of secular planetary evolution (e.g., McGovern et al, 2002), related to cooling and thickening of the lithosphere (Ruiz, 2014). This can be so because the observed T e values derive from the state of the lithosphere when the topography was formed (or, in the case of the T e calculated from spectral methods, when the relation between topography and gravity was established) (Watts, 2001).…”