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The habitability of a stagnant-lid Earth.

Authors :
Tosi, N.
Godolt, M.
Stracke, B.
Ruedas, T.
Grenfell, J. L.
H7#246;ning, D.
Nikolaou, A.
Plesa, A. -C.
Breuer, D.
Spohn, T.
Source :
Astronomy & Astrophysics / Astronomie et Astrophysique; Sep2017, Vol. 605, p1-21, 21p
Publication Year :
2017

Abstract

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<subscript>2</subscript>O and CO<subscript>2</subscript>, 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<subscript>2</subscript>O and CO<subscript>2</subscript> 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<subscript>2</subscript>O and CO<subscript>2</subscript>. The maximal partial pressure of H<subscript>2</subscript>O is limited to a few tens of bars by the high solubility of water in basaltic melts. The low solubility of CO<subscript>2</subscript> 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<subscript>2</subscript>, 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<subscript>2</subscript>, can vary in a non-monotonic way depending on the extent of the outgassed H<subscript>2</subscript>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. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00046361
Volume :
605
Database :
Complementary Index
Journal :
Astronomy & Astrophysics / Astronomie et Astrophysique
Publication Type :
Academic Journal
Accession number :
127655080
Full Text :
https://doi.org/10.1051/0004-6361/201730728