Comparing Tropospheric Water Vapor Isotopic Distribution and Controls on Earth and Mars

Isotopic analysis serves as a critical tool in understanding the complexities of the water cycle and quantifying the influence of distinct atmospheric processes.This research focuses on the spatio-temporal distribution of the HDO/H2O ratio in water vapor on Earth and Mars, identifying the processes that control these variations.Utilizing isotopic data from General Circulation Model LMDZ simulations for Earth and Planetary Climate Model (PCM) simulations for Mars, we investigate the similarities and differences in water vapor transport and phase changes within each planet's atmosphere. Key findings include a marked isotopic enrichment from ice sublimation in both planets, with a stronger effect observed on Mars due to longer crystal residence times. In contrast, Earth exhibits a buffering effect by the near-surface ocean not present on Mars. Our hypothesis that a unified conceptual framework can interpret isotopic distributions on both planets is supported, suggesting shared fundamental processes with adaptations to each planet's unique conditions.This comparative analysis not only highlights the similarities and differences in the water cycles of Earth and Mars, but also demonstates the adaptability of our conceptual framework to various planetary environments. These insights enhance our comprehension of planetary hydrological cycles and contribute to a deeper understanding of their underlying microphysical mechanisms.