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  Land Fraction Diversity on Earth-like Planets and Implications for Their Habitability

Höning, D., Spohn, T. (2023): Land Fraction Diversity on Earth-like Planets and Implications for Their Habitability. - Astrobiology, 23, 4, 372-394.
https://doi.org/10.1089/ast.2022.0070

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Höning, Dennis1, Author              
Spohn, Tilman2, Author
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1Potsdam Institute for Climate Impact Research, Potsdam, ou_persistent13              
2External Organizations, ou_persistent22              

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 Abstract: A balanced ratio of ocean to land is believed to be essential for an Earth-like biosphere, and one may conjecture that plate-tectonics planets should be similar in geological properties. After all, the volume of continental crust evolves toward an equilibrium between production and erosion. If the interior thermal states of Earth-sized exoplanets are similar to those of Earth—a straightforward assumption due to the temperature dependence of mantle viscosity—one might expect a similar equilibrium between continental production and erosion to establish, and hence a similar land fraction. We show that this conjecture is not likely to be true. Positive feedback associated with the coupled mantle water—continental crust cycle may rather lead to a manifold of three possible planets, depending on their early history: a land planet, an ocean planet, and a balanced Earth-like planet. In addition, thermal blanketing of the interior by the continents enhances the sensitivity of continental growth to its history and, eventually, to initial conditions. Much of the blanketing effect is, however, compensated by mantle depletion in radioactive elements. A model of the long-term carbonate–silicate cycle shows the land and the ocean planets to differ by about 5 K in average surface temperature. A larger continental surface fraction results both in higher weathering rates and enhanced outgassing, partly compensating each other. Still, the land planet is expected to have a substantially dryer, colder, and harsher climate possibly with extended cold deserts in comparison with the ocean planet and with the present-day Earth. Using a model of balancing water availability and nutrients from continental crust weathering, we find the bioproductivity and the biomass of both the land and ocean planets to be reduced by a third to half of those of Earth. The biosphere on these planets might not be substantial enough to produce a supply of free oxygen.

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Language(s): eng - English
 Dates: 2023-03-312023-04-01
 Publication Status: Finally published
 Pages: 23
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1089/ast.2022.0070
MDB-ID: pending
PIKDOMAIN: RD1 - Earth System Analysis
Organisational keyword: RD1 - Earth System Analysis
Working Group: Long-Term Dynamics of the Earth System
OATYPE: Hybrid Open Access
 Degree: -

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Title: Astrobiology
Source Genre: Journal, SCI, Scopus, p3
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Pages: - Volume / Issue: 23 (4) Sequence Number: - Start / End Page: 372 - 394 Identifier: CoNE: https://publications.pik-potsdam.de/cone/journals/resource/journals40
Publisher: Mary Ann Liebert