a) Composite image showing the comet’s nucleus at 1.095 μm, and the water column density superimposed. Contour lines in the coma indicate the retrieved H₂O column density values ranging from 2 × 10²⁰ m^-2 (blue line) to 5 × 10²⁰ m^-2 (red line). The image number is I1_00387442903, acquired on 12 April 2015, and shown in Fig. 6e. The observed jets are caused by dust particles, while water is exclusively located in the coma above the neck, as shown in Panel c). The red and green boxes indicate the pixels averaged to provide the mean spectra seen in Fig. 2a, b, respectively. b) CO₂ to H₂O ratio for the considered VIRTIS image. c) Water column density of the VIRTIS image, obtained as explained in the text. The dashed line indicates the radial direction considered for the profiles in Fig. 5a. d) CO₂ column density of the VIRTIS image, obtained as explained in the text. The dashed line indicates the radial profile considered for the profiles in Fig. 5b.