a) Map of the comet’s regions, identified on the surface as reported by Thomas et al. (2015). b) Cylindrical map of CO₂ to H₂O column density ratio, obtained using the data from the surface to 6 km from the nucleus. The values are provided as the percentage of the CO₂ content with respect to the H₂O one. Points having a CO₂/H₂O column density ratio exceeding the maximum value indicated by the colour ramp are marked in white. c) H₂O column density map obtained considering the data at a tangent altitude in the range 0 to 6 km from the nucleus. d) The same as c), for CO₂.