Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2023

The role of magma oceans in maintaining surface water on rocky planets orbiting M-dwarfs

Keavin Moore
  • Fonction : Auteur
Nicolas B. Cowan
  • Fonction : Auteur

Résumé

Earth-like planets orbiting M-dwarf stars, M-Earths, are currently the best targets to search for signatures of life. Life as we know it requires water. The habitability of M-Earths is jeopardized by water loss to space: high flux from young M-dwarf stars can drive the loss of 3-20 Earth oceans from otherwise habitable planets. We develop a 0-D box model for Earth-mass terrestrial exoplanets, orbiting within the habitable zone, which tracks water loss to space and exchange between reservoirs during an early surface magma ocean phase and the longer deep-water cycling phase. A key feature is the duration of the surface magma ocean, assumed concurrent with the runaway greenhouse. This time-scale can discriminate between desiccated planets, planets with desiccated mantles but substantial surface water, and planets with significant water sequestered in the mantle. A longer-lived surface magma ocean helps M-Earths retain water: dissolution of water in the magma provides a barrier against significant loss to space during the earliest, most active stage of the host M-dwarf, depending on the water saturation limit of the magma. Although a short-lived basal magma ocean can be beneficial to surface habitability, a long-lived basal magma ocean may sequester significant water in the mantle at the detriment of surface habitability. We find that magma oceans and deep-water cycling can maintain or recover habitable surface conditions on Earth-like planets at the inner edge of the habitable zone around late M-dwarf stars - these planets would otherwise be desiccated if they form with less than ~10 terrestrial oceans of water.

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insu-04462223 , version 1 (17-02-2024)

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Keavin Moore, Nicolas B. Cowan, Charles-Édouard Boukaré. The role of magma oceans in maintaining surface water on rocky planets orbiting M-dwarfs. Monthly Notices of the Royal Astronomical Society, 2023, 526, pp.6235-6247. ⟨10.1093/mnras/stad3138⟩. ⟨insu-04462223⟩
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