硫光化学观测追踪岩石行星的地幔氧化还原状态
Sulfur photochemistry observationally traces mantle redox states of rocky planets
AI总结：
研究不同类型岩石行星中，脱气与光化学如何共同决定大气组成。通过耦合PROTEUS框架与化学模型模拟，发现大气组成受地幔氧化还原状态和脱气历史控制，光化学影响高层大气，其产生的SO2特征可被JWST探测，为观测提供方向。
AI中文摘要：
行星内部的挥发性物质脱气控制着岩石系外行星的次生大气组成。然而，观测表明光化学和垂直传输等非平衡过程会强烈改变热木星的化学结构。不同类型的岩石行星中哪个过程占主导，以及脱气和光化学如何共同决定大气组成仍是未解之谜。硫物种有望成为内部 - 大气耦合的示踪剂。将PROTEUS行星内部 - 大气演化建模框架与FastChem和VULCAN两个化学模型耦合进行后处理化学计算。进行了一系列行星演化模拟，比较了热化学平衡、仅垂直传输以及垂直传输加光化学情况下的大气组成。结果表明，即使包含非平衡化学，大气的整体组成仍受地幔氧化还原状态和脱气历史控制。光化学影响高层大气，强烈消耗中性挥发性物质并增强自由基。合成发射光谱显示，光化学产生的SO2在特定波段有吸收特征，可被JWST探测到，这促使开展有针对性的观测活动。
英文摘要：
Volatile outgassing from planetary interiors controls the composition of rocky exoplanets' secondary atmospheres. However, observations indicate that disequilibrium processes, such as photochemistry and vertical transport, can strongly alter the chemical structure of Hot Jupiters. Which process dominates under different types of rocky planets, and how outgassing and photochemistry jointly determine the atmospheric composition, remain open questions. Sulfur species are promising tracers of interior-atmosphere coupling because their atmospheric abundances are sensitive to both mantle redox state and stellar irradiation. The PROTEUS planetary interior-atmosphere evolution modelling framework is coupled to two chemical models, FastChem and VULCAN, for post-processed chemistry calculations. We run a grid of planetary evolution simulations spanning diverse mantle redox states, instellation fluxes, and Solar versus M-star host-star spectra. For each case, we compare atmospheric compositions under thermochemical equilibrium, only vertical transport, and vertical transport plus photochemistry. The bulk atmospheric composition remains controlled by the redox state of the mantle and outgassing history, even when disequilibrium chemistry is included. Reduced mantles produce atmospheres rich in H2, and oxidised mantles are dominated by CO2. Photochemistry affects the upper atmosphere, strongly depleting neutral volatiles and enhancing radicals, especially for highly irradiated cases. SO2 is strongly enhanced at intermediate-to-oxidised redox states. Synthetic emission spectra show that photochemical SO2 can generate absorption features at 4 um and at 7.3 / 8.7 um, reaching ~60 ppm and ~100 ppm, before sequentially returning to the outgassed signatures of ~30 ppm and ~50 ppm for the oxidised mantle redox state. These signatures are detectable with JWST, motivating targeted observational campaigns.
