Theoretical\nInsights into Gas Migration Within Ice\non Earth and Icy Celestial Bodies

Atmospheric gases trapped in icy environments, such as\nEarth’s\npolar regions and Jupiter’s moon Europa, offer a unique opportunity\nto explore paleoclimate and astrogeological history. While previous\nstudies have addressed the diffusive behaviors of these gases and\ntheir implications for paleoclimatological and geochronological reconstructions,\nthe underlying mechanisms of gas migration in ice remain largely unexplored.\nAchieving an atomistic-level understanding of gas migration is therefore\nessential for improving our knowledge of the long-term behavior of\ngases in icy environments. In this study, we investigated the migration\nof noble gases encapsulated in isolated air bubbles within bulk ice\nusing density functional theory calculations. We focused on both the\ndissolution at the gas–ice interface and the subsequent molecular\ndiffusion through the ice lattice. Our results show that energy barriers\nfor dissolution and molecular diffusion increase almost linearly with\natomic size, leading to nonlinear, exponential-like decreases in solubility\nand diffusivity, due to their Arrhenius behavior in relation to the\ncorresponding energy barriers. These energy barriers primarily arise\nfrom the structural distortions in the ice lattice, as it accommodates\nnoble gas atoms. Additionally, our findings indicate that dissolution\nis energetically both more demanding and slower than molecular diffusion,\nmaking it the rate-limiting step in gas migration through ice. These\nfindings provide valuable insights into gas migration and fractionation\nmechanisms in Earth’s polar ice, highlighting the importance\nof incorporating atomic-level interactions into geochronological models.\nBy deepening our fundamental understanding of gas mobility, this work\nnot only advances methodologies for analyzing Earth’s ice but\nalso broadens our perspective on extraterrestrial icy environments,\nwith potential implications for the search for life-supporting conditions\nbeyond Earth.