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Inefficient Water Degassing Inhibits Ocean Formation on Rocky Planets: An Insight from Self-Consistent Mantle Degassing Models

Miyazaki, Yoshinori and Korenaga, Jun (2022) Inefficient Water Degassing Inhibits Ocean Formation on Rocky Planets: An Insight from Self-Consistent Mantle Degassing Models. Astrobiology, 22 (6). pp. 713-734. ISSN 1531-1074. doi:10.1089/ast.2021.0126.

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A sufficient amount of water is required at the surface to develop water oceans. A significant fraction of water, however, remains in the mantle during magma ocean solidification, and thus the existence of water oceans is not guaranteed even for exoplanets located in the habitable zone. To discuss the likelihood of ocean formation, we built two models to predict the rate of mantle degassing during the magma ocean stage and the subsequent solid-state convection stage. We find that planets with low H₂O/CO₂ ratios would not have a sufficient amount of surface water to develop water oceans immediately after magma ocean solidification, and the majority of the water inventory would be retained in the mantle during their subsequent evolution regardless of planetary size. This is because oceanless planets are likely to operate under stagnant lid convection, and for such planets, dehydration stiffening of the depleted lithospheric mantle would limit the rate of mantle degassing. In contrast, a significant fraction of CO₂ would already be degassed during magma ocean solidification. With a strong greenhouse effect, all surface water would exist as vapor, and water oceans may be absent throughout planetary evolution. Volatile concentrations in the bulk silicate Earth are close to the threshold amount for ocean formation, so if Venus shared similar concentrations, small differences in solar radiation may explain the divergent evolutionary paths of Earth and Venus.

Item Type:Article
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URLURL TypeDescription
Miyazaki, Yoshinori0000-0001-8325-8549
Korenaga, Jun0000-0002-4785-2273
Additional Information:© 2022, Mary Ann Liebert, Inc. Submitted 7 August 2021. Accepted 21 January 2022. Online Ahead of Print: March 1, 2022. This article is benefited from the comments by Dan Bower, Darius Modirrousta-Galian, and two anonymous reviewers. This work was sponsored by the U.S. National Aeronautics and Space Administration under Cooperative Agreement No. 80NSSC19M0069 issued through the Science Mission Directorate and the National Science Foundation under grant EAR-1753916, and in part by the facilities and staff of the Yale University Faculty of Arts and Sciences High Performance Computing Center. Y.M. was supported by the Stanback Postdoctoral Fellowship from Caltech Center for Comparative Planetary Evolution.
Funding AgencyGrant Number
Yale UniversityUNSPECIFIED
Foster and Coco Stanback Postdoctoral FellowshipUNSPECIFIED
Subject Keywords:Habitability; Magma ocean; Ocean formation
Issue or Number:6
Record Number:CaltechAUTHORS:20220322-742498000
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Official Citation:Inefficient Water Degassing Inhibits Ocean Formation on Rocky Planets: An Insight from Self-Consistent Mantle Degassing Models. Yoshinori Miyazaki and Jun Korenaga. Astrobiology 2022 22:6, 713-734; DOI: 10.1089/ast.2021.0126
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114010
Deposited By: George Porter
Deposited On:23 Mar 2022 14:39
Last Modified:29 Jun 2022 21:27

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