Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Hahn, Brian C.

Jiménez Díaz, Alberto

López, Valle

McGovern, Patrick J.

Ruiz Pérez, Javier

Tejero López, Rosa

Williams, Jean-Pierre

Docta Complutense

The heat flow history of Mars from lithospheric strength Javier Ruiz (1), Patrick J. McGovern (2), Alberto Jiménez-Díaz (1), Valle López (3), Jean-Pierre Williams (4), Brian C. Hahn (5), Rosa Tejero (1,3). (1) Departamento de Geodinámica, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid, 28040 Madrid, Spain (jaruiz@geo.ucm.es). (2) Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA. (3) Instituto de Geociencias, CSIC-UCM, 28040 Madrid, Spain. (4) Department of Earth and Space Sciences, University of California, Los Angeles, CA 90095, USA. (5) Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA.  Lithospheric strength can be used to estimate the heat flow at the time when a given region was deformed, allowing us to constrain the thermal evolution of a planetary body [1,2]. Here we report carefully calculated paleo-heat flow for 22 martian regions of different periods and geological context (Fig. 1), derived from effective elastic thicknesses [1-5] or from faulting depth beneath large thrust faults [6,7], by considering regional radioactive element abundances [8], and realistic thermal conductivities for the crust and mantle lithosphere [9,10]. For the calculations from the effective elastic thickness of the lithosphere we also consider the respective contributions of crust and mantle lithosphere to the total lithospheric strength, along with adequate flow laws [see 10]. The obtained surface heat flows (Figure 2) are in general lower than the equivalent radioactive heat production of Mars in each time, suggesting a limited contribution from secular cooling to the heat flow during the majority of the history of Mars. This is contrary to the predictions from the majority of thermal history models [e.g., 11]. Moreover, the interior of Mars could even have been heating up during part of the thermal history of the planet. Our results can also be interpreted in terms of the Urey number Ur, the ratio of the internal heat production to the total surface heat loss in a planet. Figure 2 indicates very low heat flows relative to expected heat output, consistent with very little secular cooling, i.e., a bulk-Mars Ur for Mars approaching 1.0 or perhaps even exceeding that value. Current estimates of the bulk-Earth Ur are in the range 0.35-0.53 [e.g., 12,13], and somewhat higher (but usually < 0.75) values are predicted for most Martian thermal history models. Our results would be indicative of less efficient mantle convection than commonly thought (perhaps related to stagnant lid convection with inefficient volatile cycling) and/or a reduced contribution from fossil heat to the surface heat flow, which would result in a lower heat flow from the convective mantle, and possibly elevated lower mantle and core temperatures. Also, there is evidence favoring a heterogeneous heat flow depending on the geological province (volcanic versus non-volcanic provinces), although it cannot presently be definitively demonstrated. Moreover, if the interior of Mars is in fact heating up (Ur > 1), there is the potential for a future increase in mantle convective vigor and/or melting, and there may ultimately be an increasing of volcanic and tectonic activity. References [1] McGovern, P.J. et al., JGR 107, 5136, 2002. [2] McGovern, P.J. et al., JGR. 109, E07007, 2004. [3] Grott, M. et al., GRL 32, L21201, 2005. [4] Phillips, R.J., et al., Science 320, 1182-1185, 2008. [5] Ritzer, J.A. and Hauck, S.A. Icarus 201, 528-539, 2009. [6] Grott, M. et al., Icarus 186, 517-526, 2007. [7] Ruiz, J. et al., EPSL 270, 1-12, 2009. [8] Hahn, B.C. and McLennan, S.M., LPSC 39, abstract 2032, 2008. [9] Beardsmore, G.R. and Cull, J.P. Crustal heat flow. A guide to measurement and modelling, Cambridge University Press, Cambridge, 324 pp, 2001. [10] McKenzie, D. Et al., EPSL 233, 337-349, 2005. [11] Hauck, S.A. and Phillips, R.J. JGR 107, 5052, 2002. [12] Jaupart, C. et al., Temperatures, Heat and Energy in the Mantle of the Earth. In: Bercovici, S. (Ed.), Treatise on Geophysics vol. 7: Mantle Dynamics. Elsevier, Amsterdam, pp. 253-303, 2007. [13] Korenaga, J. Rev Geophys. 46, 1-32, 2008. [14] Wänke, H. and Dreibus, G. Phil. Trans. R. Soc. London A 325, 545-557, 1988.   EPSC AbstractsVol. 6, EPSC-DPS2011-1203, 2011EPSC-DPS Joint Meeting 2011c© Author(s) 2011Figure 1. MOLA topography map showing the analyzed regions.    Figure 2. Upper (red) and lower (blue) limits for the surface heat flows for regions of Figure 1. For several regions only upper or lower limit is obtained, since lower or upper limit effective elastic thickness is not available. Curves and horizontal lines indicate uncertainty related to surface age (and hence also to radioactive heating in the lithosphere), not to temporal evolution. The black curves show surface heat flows for three values of the Urey number (the ratio of the internal heat production to the total surface heat loss in a planet), calculated according to the composition model of [14]. The curve labeled “Radioactive (Ur = 1)” corresponds to the average surface heat flow which is equivalent to the total radioactive heat production of Mars.  

English

The heat flow history of Mars from lithospheric strength

https://docta.ucm.es/bitstreams/6742a1f9-91b0-4295-822f-143c0637c218/download

The heat flow history of Mars from lithospheric strength

Abstract

Similar works

Full text

Available Versions

Docta Complutense