Inner disk chemistry and the effects of drifting icy grains: the case of CO2.

The efficiency of radial transport of icy solid material from the outer disk to the inner disk is currently unconstrained. Efficient radial transport of icy dust grains could significantly alter the composition of the gas in the inner disk. Using a 1D viscous disk model, the effects of accretion flow and radial drift on the abundance of CO2 in the inner regions of protoplantary disks have been modelled and the results and implications of these models will be presented. Models show, that even without radial drift, CO2 is quickly added to the inner disk equilibriating the inner disk CO2 abundance with the ice abundance. This predicts CO2 abundances up to three orders of magnitudes higher than the abundances inferred from infrared observations by Spitzer. A range of potential physical and chemical mechanisms to try to explain this discrepancy as are discussed. Prediction are made for JWST-MIRI observations to discern the different scenarios.