On the equilibrium limit of liquid stability in pressurized aqueous systems

Summary

The study introduces the concept of "cenotectic," the temperature limit of liquid stability in pressurized aqueous systems, and measures it for several binary aqueous brines using isochoric freezing and melting.

Highlights

• The cenotectic point represents the lowest possible temperature at which a given aqueous liquid phase may remain stable at equilibrium under any P-T-x conditions.
• The study uses isochoric freezing and melting to measure the cenotectic points for several binary aqueous brines.
• The results have implications for ocean worlds within our solar system and cold ocean exoplanets.
• The cenotectic concept has applications in planetary science, particularly for icy moons and water-rich exoplanets.
• The study estimates thermodynamic limits on ice crust thickness and final ocean depth using measured cenotectic pressures.
• The findings provide a generalized thermodynamic perspective on the cenotectic point.
• The cenotectic point is a fundamental property of the system, representing the absolute limit of liquid stability.

Key Insights

• The cenotectic point is a critical concept in understanding the thermodynamic behavior of aqueous systems under pressure, and its measurement has significant implications for various fields, including planetary science and engineering.
• The study's results suggest that the cenotectic point is primarily dictated by the thermodynamics of water/ice in binary salt systems, leading to a 22K rule of thumb for the temperature difference between the 0.1MPa univariant eutectic and the cenotectic.
• The formation of new stable hydrates at thermodynamic equilibrium will increase the cenotectic temperature, while the formation of metastable new hydrates will decrease it, highlighting the complex interplay between thermodynamics and kinetics in these systems.
• The cenotectic concept has far-reaching implications for our understanding of the habitability of icy moons and water-rich exoplanets, as it controls the stability of brines in the icy crust and the circulation of salty fluids.
• The study's findings provide a new perspective on the "endgame" of planetary oceans, where the ocean will gradually freeze from top to bottom until complete solidification is achieved, with the cenotectic playing a central role in this process.
• The cenotectic depth, estimated using the formula zκ=Pκ=(ρg), provides the absolute maximum upper limit for the ice crust thickness if an ocean is present, and its calculation has significant implications for the study of icy moons and water-rich exoplanets.
• The study highlights the need for further research into the cenotectic concept, including the measurement of cenotectic limits for other chemical systems and the refinement of the concept itself to establish definite and fundamental limits on liquid phase equilibria.

Mindmap

Citation

Zarriz, A., Journaux, B., & Powell-Palm, M. J. (2024). On the equilibrium limit of liquid stability in pressurized aqueous systems. In Nature Communications (Vol. 15, Issue 1). Springer Science and Business Media LLC. https://doi.org/10.1038/s41467-024-54625-z