Thermal evolution of an early magma ocean in interaction with the atmosphere

LeBrun, Thomas W.; Massol, Hélène; Chassefière, Éric; Davaille, Anne; Marcq, Emmanuel; Sarda, Philippe; Leblanc, François; Brandeis, G.

doi:10.1002/jgre.20068

Cited by 216 publications

(500 citation statements)

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“…F is bracketed by the dashed (Lebrun et al, 2013) and solid lines (Solomatov et al, 1993), systematically decreasing during MO freezing as dMO decreases (upward). Accordingly, the (b) predicted progression rate of the crystallization front vMOC also decreases (latent heat of fusion is taken to be 560 kJ/kg (Solomatov, 2015), fractional crystallization very likely dominates at least for dMO < 150 km, or potentially over a much greater depth range (see text).…”

Section: Resultsmentioning

confidence: 99%

“…Note that vMOC is a function of dMO ( Figure 3) for a given cooling scenario of the MO. Diapir diameters decrease from ~100 km to ~1 km through the upper mantle, bracketed by cooling scenarios (dashed line (Lebrun et al, 2013); solid line (Solomatov et al, 1993)). Diapir sinking depths (b), here defined as the depth of thermal equilibration during sinking, depend on diapir diameter and mantle rheology according to Stokes Law (see Appendix A2).…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, short timescales imply fast turbulent convection, and hence equilibrium crystallization. MO crystallization timescales strongly depend on the nature and thickness of the proto-atmosphere, which ultimately controls the heat flux from Earth to space (Lebrun et al, 2013;Marcq, 2012). As long as some degree of chemical fractionation occurs and the MO freezes from the bottom upwards, the MO is predicted to become progressively Fe-rich as Mg-rich bridgmanite in the lower mantle (Andrault et al, 2012;Boukare et al, 2015;Fiquet et al, 2010;Nomura et al, 2011;Tateno et al, 2014), and other Mg-rich phases (mostly olivine and pyroxenes) in the upper mantle, are successively removed.…”

Section: Introductionmentioning

confidence: 99%

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Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Ballmer

Lourenço

Hirose

et al. 2017

Geochem Geophys Geosyst

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Terrestrial planets are thought to experience episode(s) of large‐scale melting early in their history. Fractionation during magma‐ocean freezing leads to unstable stratification within the related cumulate layers due to progressive iron enrichment upward, but the effects of incremental cumulate overturns during MO crystallization remain to be explored. Here, we use geodynamic models with a moving‐boundary approach to study convection and mixing within the growing cumulate layer, and thereafter within the fully crystallized mantle. For fractional crystallization, cumulates are efficiently stirred due to subsequent incremental overturns, except for strongly iron‐enriched late‐stage cumulates, which persist as a stably stratified layer at the base of the mantle for billions of years. Less extreme crystallization scenarios can lead to somewhat more subtle stratification. In any case, the long‐term preservation of at least a thin layer of extremely enriched cumulates with Fe# > 0.4, as predicted by all our models, is inconsistent with seismic constraints. Based on scaling relationships, however, we infer that final‐stage Fe‐rich magma‐ocean cumulates originally formed near the surface should have overturned as small diapirs, and hence undergone melting and reaction with the host rock during sinking. The resulting moderately iron‐enriched metasomatized/hybrid rock assemblages should have accumulated at the base of the mantle, potentially fed an intermittent basal magma ocean, and be preserved through the present‐day. Such moderately iron‐enriched rock assemblages can reconcile the physical properties of the large low shear‐wave velocity provinces in the present‐day lower mantle. Thus, we reveal Hadean melting and rock‐reaction processes by integrating magma‐ocean crystallization models with the seismic‐tomography snapshot.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Ballmer

Lourenço

Hirose

et al. 2017

Geochem Geophys Geosyst

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“…Elkins-Tanton 2008; Lebrun et al 2013) has a potentially much more significant influence on the outcomes of our models. In contrast to previous studies, no matter whether based on platetectonic or stagnant-lid convection, our models account for the effect of growing atmospheric pressure on the outgassing of H 2 O and CO 2 (see Figs.…”

Section: Discussionmentioning

confidence: 99%

The habitability of a stagnant-lid Earth

Tosi

Godolt

Stracke

et al. 2017

A&A

128

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Context. Plate tectonics is considered a fundamental component for the habitability of the Earth. Yet whether it is a recurrent feature of terrestrial bodies orbiting other stars or unique to the Earth is unknown. The stagnant lid may rather be the most common tectonic expression on such bodies. Aims. To understand whether a stagnant-lid planet can be habitable, i.e. host liquid water at its surface, we model the thermal evolution of the mantle, volcanic outgassing of H 2 O and CO 2 , and resulting climate of an Earth-like planet lacking plate tectonics. Methods. We used a 1D model of parameterized convection to simulate the evolution of melt generation and the build-up of an atmosphere of H 2 O and CO 2 over 4.5 Gyr. We then employed a 1D radiative-convective atmosphere model to calculate the global mean atmospheric temperature and the boundaries of the habitable zone (HZ).Results. The evolution of the interior is characterized by the initial production of a large amount of partial melt accompanied by a rapid outgassing of H 2 O and CO 2 . The maximal partial pressure of H 2 O is limited to a few tens of bars by the high solubility of water in basaltic melts. The low solubility of CO 2 instead causes most of the carbon to be outgassed, with partial pressures that vary from 1 bar or less if reducing conditions are assumed for the mantle to 100-200 bar for oxidizing conditions. At 1 au, the obtained temperatures generally allow for liquid water on the surface nearly over the entire evolution. While the outer edge of the HZ is mostly influenced by the amount of outgassed CO 2 , the inner edge presents a more complex behaviour that is dependent on the partial pressures of both gases. Conclusions. At 1 au, the stagnant-lid planet considered would be regarded as habitable. The width of the HZ at the end of the evolution, albeit influenced by the amount of outgassed CO 2 , can vary in a non-monotonic way depending on the extent of the outgassed H 2 O reservoir. Our results suggest that stagnant-lid planets can be habitable over geological timescales and that joint modelling of interior evolution, volcanic outgassing, and accompanying climate is necessary to robustly characterize planetary habitability.

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“…This is due to a lower value of atmospheric pressure. More detailed discussion can be found in [9,10]. …”

Section: Bio Web Of Conferences Bioconfmentioning

confidence: 99%

Thermal evolution of an early magma ocean in interaction with the atmosphere: conditions for the condensation of a water ocean

LeBrun

Massol

Chassefière

et al. 2014

BIO Web of Conferences

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Abstract. The thermal evolution of magma oceans produced by collision with giant impactors late in accretion is expected to depend on the composition and structure of the atmosphere through the greenhouse effect of CO 2 and H 2 O released from the magma during its crystallization. We developed a 1D parameterized convection model of a magma ocean coupled with a 1D radiative convective model of the atmosphere. We conducted a parametric study and described the influences of some important parameters such as the Sun-planet distance. Our results suggest that a steam atmosphere delays the end of the magma ocean phase by typically 1 Myr. Water vapor condenses to an ocean after 0.1 Myr, 1.5 Myr and 10 Myr for, respectively, Mars, Earth and Venus. This time would be virtually infinite for an Earth-sized planet located at less than 0.66 AU from the Sun. So there are conditions such as no water ocean is formed on Venus. Moreover, for Mars and Earth, water ocean formation time scales are shorter than typical time gaps between major impacts. This implies that successive water oceans may have developed during accretion, making easier the loss of their atmospheres by impact erosion. Objectives and resultsOne of the important objectives of the present work is to better understand the conditions and timing of the formation of the terrestrial ocean of water, and why such an ocean did not form on Venus, or possibly formed at an early stage but later evaporated due to the increasing luminosity of the young Sun. The presence of an early massive atmosphere of water vapor on Venus, which further escaped to space, and/or was trapped in the interior under the form of hydrates, is generally considered to have initiated the strong greenhouse effect observed today [1,2]. This massive H 2 O atmosphere may have resulted, (i) either from the evaporation of a primordial water ocean, followed by hydrodynamic escape of hydrogen [3], or (ii) from the outgassing of the primordial magma ocean, not necessarily followed by the formation of a (transient) water ocean [4]. Determining, through a comparative modeling approach applied to the three terrestrial planets Mars, Earth and Venus if a water ocean ever condensed on Venus and, if so, how long this ocean survived, is one of the major challenges of

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Thermal evolution of an early magma ocean in interaction with the atmosphere

Cited by 216 publications

References 84 publications

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

The habitability of a stagnant-lid Earth

Thermal evolution of an early magma ocean in interaction with the atmosphere: conditions for the condensation of a water ocean

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