Theoretical Insights into Gas Migration Within Ice on Earth and Icy Celestial Bodies

Abstract

Atmospheric gases trapped in icy environments, such as Earth's polar regions and Jupiter's moon Europa, offer a unique opportunity to explore paleoclimate and astrogeological history. While previous studies have addressed the diffusive behaviors of these gases and their implications for paleoclimatological and geochronological reconstructions, the underlying mechanisms of gas migration in ice remain largely unexplored. Achieving an atomistic-level understanding of gas migration is therefore essential for improving our knowledge of the long-term behavior of gases in icy environments. In this study, we investigated the migration of noble gases encapsulated in isolated air bubbles within bulk ice using density functional theory calculations. We focused on both the dissolution at the gas-ice interface and the subsequent molecular diffusion through the ice lattice. Our results show that energy barriers for dissolution and molecular diffusion increase almost linearly with atomic size, leading to nonlinear, exponential-like decreases in solubility and diffusivity, due to their Arrhenius behavior in relation to the corresponding energy barriers. These energy barriers primarily arise from the structural distortions in the ice lattice, as it accommodates noble gas atoms. Additionally, our findings indicate that dissolution is energetically both more demanding and slower than molecular diffusion, making it the rate-limiting step in gas migration through ice. These findings provide valuable insights into gas migration and fractionation mechanisms in Earth's polar ice, highlighting the importance of incorporating atomic-level interactions into geochronological models. By deepening our fundamental understanding of gas mobility, this work not only advances methodologies for analyzing Earth's ice but also broadens our perspective on extraterrestrial icy environments, with potential implications for the search for life-supporting conditions beyond Earth.