Column densities as a function of time after the SL9 impacts (1994) for CO, H₂O, and CO₂. Model A results in the light green, cyan, and orange curves, while Model B results in the dark green, dark blue, and red ones. The offset between the two models results from the different background column resulting from the IDP source (see Sect. 3.1.1). The period covering the Odin monitoring (2002-2019) is highlighted in grey.