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Abstract Lava worlds are a potential emerging population of Super-Earths that are on close-in orbits around their host stars, with likely partially molten mantles. To date, few studies have addressed the impact of magma on the observed properties of a planet. At ambient conditions, magma is less dense than solid rock; however, it is also more compressible with increasing pressure. Therefore, it is unclear how large-scale magma oceans affect planet observables, such as bulk density. We updateExoPlex, a thermodynamically self-consistent planet interior software, to include anhydrous, hydrous (2.2 wt% H2O), and carbonated magmas (5.2 wt% CO2). We find that Earth-like planets with magma oceans larger than ∼1.5R⊕and ∼3.2M⊕are modestly denser than an equivalent-mass solid planet. From our model, three classes of mantle structures emerge for magma ocean planets: (1) a mantle magma ocean, (2) a surface magma ocean, and (3) one consisting of a surface magma ocean, a solid rock layer, and a basal magma ocean. The class of planets in which a basal magma ocean is present may sequester dissolved volatiles on billion-year timescales, in which a 4M⊕mass planet can trap more than 130 times the mass of water than in Earth’s present-day oceans and 1000 times the carbon in the Earth’s surface and crust.
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Constraining the Volume of Earth's Early Oceans With a Temperature‐Dependent Mantle Water Storage Capacity Model
Abstract The water content in Earth's mantle today remains poorly constrained, but the bulk water storage capacity in the solid mantle can be quantified based on experimental data and may amount to a few times the modern surface ocean mass (OM). An appreciation of the mantle water storage capacity is indispensable to our understanding of how water may have cycled between the surface and mantle reservoirs and changed the volume of the oceans through time. In this study, we parameterized high pressure‐temperature experimental data on water storage capacities in major rock‐forming minerals to track the bulk water storage capacity in Earth's solid mantle as a function of temperature. We find that the mantle water storage capacity decreases as mantle potential temperature (Tp) increases, and its estimated value depends on the water storage capacity of bridgmanite in the lower mantle: 1.86–4.41 OM with a median of 2.29 OM for today (Tp = 1600 K), and 0.52–1.69 OM with a median of 0.72 OM for the early Earth's solid mantle (for aTpthat was 300 K higher). An increase inTpby 200–300 K results in a decrease in the mantle water storage capacity by – OM. We explored how the volume of early oceans may have controlled sea level during the early Archean (4–3.2 Ga) with some additional assumptions about early continents. We found that more voluminous surface oceans might have existed if the actual mantle water content today is > 0.3–0.8 OM and the early ArcheanTpwas ≥1900 K.
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- PAR ID:
- 10386707
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- AGU Advances
- Volume:
- 2
- Issue:
- 1
- ISSN:
- 2576-604X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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