Speaker
Description
The ARIEL space mission will characterize the atmospheres of hundreds of exoplanets, pushing beyond the canonical hot Jupiters into cooler regimes where longer chemical timescales amplify the roles of transport and photochemistry. In these atmospheres, disequilibrium processes are expected to leave measurable imprints on molecules central to ARIEL's science case, such as H2O, CO2, and CH4, while enhancing the abundances of secondary absorbers such as NH3, HCN, and C2H2.
Using the classical HD 209458 b as a benchmark, we quantify how horizontal mixing, vertical transport, and photochemistry jointly shape transmission spectra. We couple 2D photochemical-transport simulations (VULCAN 2D) with forward radiative transfer modelling (petitRADTRANS) to generate synthetic JWST transmission spectra, enabling direct comparison with existing observational data and providing a framework scalable to ARIEL targets.
We investigate how the interplay between dynamical and chemical timescales alters the abundances of key molecules such as CH4, promoting the formation of species such as HCN and C2H2. For instance, C2H2 features strengthen under enhanced photochemistry but weaken with stronger vertical mixing. We also find that the presence of C2H2 is consistent with solar C/O at low metallicity, while enhanced abundances also emerge at higher C/O ratios across a broader range of metallicities. In contrast, species such as CO2 act as robust metallicity tracers that are largely insensitive to disequilibrium chemistry effects. By directly linking multidimensional disequilibrium chemistry to observable infrared signatures, we show how these processes imprint distinct, and potentially degenerate, features on infrared spectra.