CO₂ amount on Venus constrained by a criterion of topographic-greenhouse instability

Which mechanism determines the planetary atmospheric inventories of various gases is an important problem. It has been suggested that Venus' atmospheric CO₂ abundance is controlled or buffered by carbonation reaction on the surface (carbonate buffer). According to this hypothesis, the formation or decomposition of carbonate stabilizes atmospheric CO₂ concentration. However, the amount of carbonate existing on the Venus' surface is not established yet. Using a stability analysis that combines the greenhouse effect, carbonation reaction, and topography, we place an upper limit to carbonate on Venus. This upper limit of carbonate is only about 4 bar of CO₂ and is much smaller than the amount of CO₂ in the atmosphere. This suggests that the present CO₂ concentration in Venus' atmosphere is not controlled by the carbonation reaction but by the total abundance of CO₂ in near surface layers.