Upper row: reproduction of Fig. 2, observed ice optical depth mapped images. Lower row: benchmark model optical depth images of the disc in H₂O, CO₂, and CO, as derived at 3.0, 4.26, 4.67 μm calculated against the reference continuum intensities taken at 3.7, 4.32, 4.72 μm, respectively. Over-plotted white contours show the flux intensities at the band centres, normalised to their maximum in the map. The last contour is at 5% from the maximum which is approximately the limit achieved in the observations.