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Outgassing on stagnant-lid super-Earths


Dorn, C; Noack, L; Rozel, A B (2018). Outgassing on stagnant-lid super-Earths. Astronomy and Astrophysics, 614:A18.

Abstract

Aims. We explore volcanic CO2-outgassing on purely rocky, stagnant-lid exoplanets of different interior structures, compositions, thermal states, and age. We focus on planets in the mass range of 1–8 M⊕ (Earth masses). We derive scaling laws to quantify first- and second-order influences of these parameters on volcanic outgassing after 4.5 Gyr of evolution.
Methods. Given commonly observed astrophysical data of super-Earths, we identify a range of possible interior structures and compositions by employing Bayesian inference modeling. The astrophysical data comprise mass, radius, and bulk compositional constraints; ratios of refractory element abundances are assumed to be similar to stellar ratios. The identified interiors are subsequently used as input for two-dimensional (2D) convection models to study partial melting, depletion, and outgassing rates of CO2.
Results. In total, we model depletion and outgassing for an extensive set of more than 2300 different super-Earth cases. We find that there is a mass range for which outgassing is most efficient (~2–3 M⊕, depending on thermal state) and an upper mass where outgassing becomes very inefficient (~5–7 M⊕, depending on thermal state). At small masses (below 2–3 M⊕) outgassing positively correlates with planet mass, since it is controlled by mantle volume. At higher masses (above 2–3 M⊕), outgassing decreases with planet mass, which is due to the increasing pressure gradient that limits melting to shallower depths. In summary, depletion and outgassing are mainly influenced by planet mass and thermal state. Interior structure and composition only moderately affect outgassing rates. The majority of outgassing occurs before 4.5 Gyr, especially for planets below 3 M⊕.
Conclusions. We conclude that for stagnant-lid planets, (1) compositional and structural properties have secondary influence on outgassing compared to planet mass and thermal state, and (2) confirm that there is a mass range for which outgassing is most efficient and an upper mass limit, above which no significant outgassing can occur. Our predicted trend of CO2-atmospheric masses can be observationally tested for exoplanets. These findings and our provided scaling laws are an important step in order to provide interpretative means for upcoming missions such as JWST and E-ELT, that aim at characterizing exoplanet atmospheres.

Abstract

Aims. We explore volcanic CO2-outgassing on purely rocky, stagnant-lid exoplanets of different interior structures, compositions, thermal states, and age. We focus on planets in the mass range of 1–8 M⊕ (Earth masses). We derive scaling laws to quantify first- and second-order influences of these parameters on volcanic outgassing after 4.5 Gyr of evolution.
Methods. Given commonly observed astrophysical data of super-Earths, we identify a range of possible interior structures and compositions by employing Bayesian inference modeling. The astrophysical data comprise mass, radius, and bulk compositional constraints; ratios of refractory element abundances are assumed to be similar to stellar ratios. The identified interiors are subsequently used as input for two-dimensional (2D) convection models to study partial melting, depletion, and outgassing rates of CO2.
Results. In total, we model depletion and outgassing for an extensive set of more than 2300 different super-Earth cases. We find that there is a mass range for which outgassing is most efficient (~2–3 M⊕, depending on thermal state) and an upper mass where outgassing becomes very inefficient (~5–7 M⊕, depending on thermal state). At small masses (below 2–3 M⊕) outgassing positively correlates with planet mass, since it is controlled by mantle volume. At higher masses (above 2–3 M⊕), outgassing decreases with planet mass, which is due to the increasing pressure gradient that limits melting to shallower depths. In summary, depletion and outgassing are mainly influenced by planet mass and thermal state. Interior structure and composition only moderately affect outgassing rates. The majority of outgassing occurs before 4.5 Gyr, especially for planets below 3 M⊕.
Conclusions. We conclude that for stagnant-lid planets, (1) compositional and structural properties have secondary influence on outgassing compared to planet mass and thermal state, and (2) confirm that there is a mass range for which outgassing is most efficient and an upper mass limit, above which no significant outgassing can occur. Our predicted trend of CO2-atmospheric masses can be observationally tested for exoplanets. These findings and our provided scaling laws are an important step in order to provide interpretative means for upcoming missions such as JWST and E-ELT, that aim at characterizing exoplanet atmospheres.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:1 June 2018
Deposited On:01 Mar 2019 15:50
Last Modified:17 Sep 2019 19:39
Publisher:EDP Sciences
ISSN:0004-6361
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1051/0004-6361/201731513
Project Information:
  • : FunderSNSF
  • : Grant IDPZ00P2_174028
  • : Project TitlePlanetary Diversity
  • : FunderSNSF
  • : Grant ID200020_160120
  • : Project TitleFormation and Evolution of planetary systems
  • : FunderFP7
  • : Grant ID320639
  • : Project TitleIGEO - Integrated geodynamics: Reconciling geophysics and geochemistry

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