A New Desalination Pump Help Define the pH of Ocean Worlds

TL;DR

This paper proposes a desalination pump mechanism that can create highly acidic, low-salinity oceans on exoplanets with high-pressure ice mantles, impacting their habitability and chemical environment.

Contribution

It introduces a novel desalination pump mechanism for ocean exoplanets, specifically analyzing its effects on ocean salinity and pH, with potential applications beyond super-Earths.

Findings

Oceans can have pH levels between 2 and 4.

The desalination pump can produce extremely low salinity oceans.

Exoplanet oceans may be more acidic than previously thought.

Abstract

We study ocean exoplanets, for which the global surface ocean is separated from the rocky interior by a high-pressure ice mantle. We describe a mechanism that can pump salts out of the ocean, resulting in oceans of very low salinity. Here we focus on the H2O-NaCl system, though we discuss the application of this pump to other salts as well. We find our ocean worlds to be acidic, with a pH in the range of 2-4. We discuss and compare between the conditions found within our studied oceans and the conditions in which polyextremophiles were discovered. This work focuses on exoplanets in the super-Earth mass range (2 M_Earth), with water composing at least a few percent of their mass. Although, the principal of the desalination pump may extend beyond this mass range.