Stability of high-temperature salty ice suggests electrolyte permeability in water-rich exoplanet icy mantles

Jean-Alexis Hernandez , Razvan Caracas (1, 2) , Stéphane Labrosse (1)

1 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
2 IPGP (UMR_7154) - Institut de Physique du Globe de Paris

Electrolytes play an important role in the internal structure and dynamics of water-rich satellites and potentially water-rich exoplanets. However, in planets, the presence of a large high-pressure ice mantle is thought to hinder the exchange and transport of electrolytes between various liquid and solid deep layers. Here we show, using first-principles simulations, that up to 2.5 wt% NaCl can be dissolved in dense water ice at interior conditions of water-rich super-Earths and mini-Neptunes. The salt impurities enhance the diffusion of H atoms, extending the stability field of recently discovered superionic ice, and push towards higher pressures the transition to the stiffer ice X phase. Scaling laws for thermo-compositional convection show that salts entering the high pressure ice layer can be readily transported across. These findings suggest that the high-pressure ice mantle of water-rich exoplanets is permeable to the convective transport of electrolytes between the inner rocky core and the outer liquid layer.

Domaines: Planète et Univers [physics]

Jean-Alexis Hernandez, Razvan Caracas, Stéphane Labrosse. Stability of high-temperature salty ice suggests electrolyte permeability in water-rich exoplanet icy mantles. Nature Communications, 2022, 13, ⟨10.1038/s41467-022-30796-5⟩. ⟨insu-03748521⟩