3D spherical models of Martian mantle convection constrained by melting history

Sekhar, P. Sudam; King, Scott D.

doi:10.1016/j.epsl.2013.11.047

Cited by 23 publications

(29 citation statements)

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“…Sekhar and King () have shown that a prominent degree 2 structure of convection is observed at ∼4 Gyr if a lot of heat sources (100% in their simulations) are concentrated into the crust. Such a planform of mantle convection could explain the generation of large plumes below Tharsis and Elysium Mons.…”

Section: Discussionmentioning

confidence: 97%

“…In those models, the northern crust contains few radioelements, due to either a thin crust in both UCM and NUCM simulations, or to a low enrichment factor for the NUCM2 ones (see Appendix A). Sekhar and King (2014) have shown that a prominent degree 2 structure of convection is observed at ∼4 Gyr if a lot of heat sources (100% in their simulations) are concentrated into the crust. Such a planform of mantle convection could explain the generation of large plumes below Tharsis and Elysium Mons.…”

Section: Model Predictions On Radioelement Concentrationsmentioning

confidence: 99%

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Hemispheric Dichotomy in Lithosphere Thickness on Mars Caused by Differences in Crustal Structure and Composition

et al. 2018

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Estimates of the Martian elastic lithosphere thickness suggest small values of ∼25 km during the Noachian for the southern hemisphere and a large present‐day difference below the two polar caps (≥300 km in the north and >110 km in the south). In addition, young lava flows suggest that Mars has been volcanically active up to the recent past. We run Monte Carlo simulations using a 1‐D parameterized thermal evolution model to investigate whether a north/south hemispheric dichotomy in crustal properties and composition can explain these constraints. Our results suggest that 55–65% of the bulk radioelement content are in the crust, and most of it (43–51%) in the southern one. The southern crust can be up to 480 kg/m3 less dense than the northern one and might contain a nonnegligible proportion of felsic rocks. Our models predict a dry mantle and a wet or dry crustal rheology today. This is consistent with a mantle depleted in radioelements and volatiles. We retrieve north/south surface heat flux of 17.1–19.5 mW/m2 and 24.8–26.5 mW/m2, respectively, and a large difference in lithospheric temperatures between the two hemispheres (170–304 K in the shallow mantle). This difference could leave a signature in the seismic signals measured by the future InSight mission.

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Section: Discussionmentioning

confidence: 97%

Section: Model Predictions On Radioelement Concentrationsmentioning

confidence: 99%

Hemispheric Dichotomy in Lithosphere Thickness on Mars Caused by Differences in Crustal Structure and Composition

et al. 2018

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“…The viscosity is calculated according to the Arrhenius law for diffusion creep [ Karato et al , ], whose nondimensional form considering both temperature and depth dependence reads [e.g., Roberts and Zhong , ]

η (T, z) = \exp ((), \frac{E + zV}{T + T_{0}} - \frac{E + z_{ref} V}{T_{ref} + T_{0}}),

where E and V are the activation energy and volume, respectively, T 0 the surface temperature, and T ref and z ref the reference temperature and depth at which a reference viscosity is attained (see Table ). In some simulations we took into account a viscosity jump of a factor of 25 in the mid‐mantle as in Roberts and Zhong [], Keller and Tackley [], and, more recently, Sekhar and King [].…”

Section: Models and Methodsmentioning

confidence: 99%

Thermal evolution and Urey ratio of Mars

Plesa

Tosi

Grott

et al. 2015

J. Geophys. Res. Planets

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The upcoming InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission, to be launched in 2016, will carry out the first in situ Martian heat flux measurement, thereby providing an important baseline to constrain the present‐day heat budget of the planet and, in turn, the thermal and chemical evolution of its interior. The surface heat flux can be used to constrain the amount of heat‐producing elements present in the interior if the Urey ratio (Ur)—the planet's heat production rate divided by heat loss—is known. We used numerical simulations of mantle convection to model the thermal evolution of Mars and determine the present‐day Urey ratio for a variety of models and parameters. We found that Ur is mainly sensitive to the efficiency of mantle cooling, which is associated with the temperature dependence of the viscosity (thermostat effect), and to the abundance of long‐lived radiogenic isotopes. If the thermostat effect is efficient, as expected for the Martian mantle, assuming typical solar system values for the thorium‐uranium ratio and a bulk thorium concentration, simulations show that the present‐day Urey ratio is approximately constant, independent of model parameters. Together with an estimate of the average surface heat flux as determined by InSight, models of the amount of heat‐producing elements present in the primitive mantle can be constrained.

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“…This, in turn, strongly limits in time partial melt generation, which, under these conditions, can only occur over the first few hundred million years of evolution [ Plesa et al , ]. This picture is indeed difficult to reconcile with Mars's large volcanic provinces and long‐lasting volcanic activity, which are likely the products of billions of years of vigorous mantle convection [e.g., Li and Kiefer , ; O'Neill et al , ; Grott and Breuer , ; Sekhar and King , ].…”

Section: Introductionmentioning

confidence: 99%

Onset of solid‐state mantle convection and mixing during magma ocean solidification

et al. 2017

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The energy sources involved in the early stages of the formation of terrestrial bodies can induce partial or even complete melting of the mantle, leading to the emergence of magma oceans. The fractional crystallization of a magma ocean can cause the formation of a compositional layering that can play a fundamental role for the subsequent long‐term dynamics of the interior and for the evolution of geochemical reservoirs. In order to assess to what extent primordial compositional heterogeneities generated by magma ocean solidification can be preserved, we investigate the solidification of a whole‐mantle Martian magma ocean, and in particular the conditions that allow solid‐state convection to start mixing the mantle before solidification is completed. To this end, we performed 2‐D numerical simulations in a cylindrical geometry. We treat the liquid magma ocean in a parameterized way while we self‐consistently solve the conservation equations of thermochemical convection in the growing solid cumulates accounting for pressure‐, temperature‐, and, where it applies, melt‐dependent viscosity. By testing the effects of different cooling rates and convective vigor, we show that for a lifetime of the liquid magma ocean of 1 Myr or longer, the onset of solid‐state convection prior to complete mantle crystallization is likely and that a significant part of the compositional heterogeneities generated by fractionation can be erased by efficient mantle mixing. We discuss the consequences of our findings in relation to the formation and evolution of compositional reservoirs on Mars and on the other terrestrial bodies of the solar system.

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3D spherical models of Martian mantle convection constrained by melting history

Cited by 23 publications

References 64 publications

Hemispheric Dichotomy in Lithosphere Thickness on Mars Caused by Differences in Crustal Structure and Composition

Hemispheric Dichotomy in Lithosphere Thickness on Mars Caused by Differences in Crustal Structure and Composition

Thermal evolution and Urey ratio of Mars

Onset of solid‐state mantle convection and mixing during magma ocean solidification

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