the southeastern quadrant. This structure manifested as a ridge in the 11, 9, and 7 %/1000 ˚A contours and extended a few thousand kilometres to the SE. This trend continued into 30 September, where global spectral slopes were considerably lower, the extent of high slope regions (>11 %/1000 ˚A) were confined to the central thousand kilometres of the coma, and the structure synonymous with Fan B exhibited higher slopes further from the nucleus than surrounding regions, likely suggesting evidence of larger, longer living, or different compositions of dust particles in this region (see discussion in section 4).

Despite the significant spectral slope shift in the outer regions of the coma from August to September, the colours within 3000 km maintained relatively high slopes, from 14.6±2%/1000 ˚A on 18 August, to 12.3±1%/1000 ˚A on 31 August, and 11.2±1%/1000 ˚A on 30 September. As mentioned in subsection 3.1.1, post-perihelion observations are affected by considerable changes in viewing geometry, such as lower phase angles and an orbital plane change. These, in tandem with the orbital position of Earth, change the view geometry of the comet from side-on (preperihelion) to nearly head on (post-perihelion). With this context, we report the post-perihelion spectral slope maps in Figure 9. On 11 January, the coma exhibited large homogenous regions of high spectral slopes on the order of 14 to 18 %/1000 ˚A in the southern hemisphere, which aligned with the South Pole of 67P. Intriguingly, by 27 January and 06 February the coma slopes had decreased by around 8-10%/1000 ˚A on average. This is a large change across the matter of just a few weeks, and is contrary to the slowly evolving behaviour we saw pre-perihelion and expected post-perihelion. It could be possible that spectral slopes from 11 January are atypical of the post-perihelion trends, and we discuss this in Section 4. Unlike the pre-perihelion trend of bluer spectral slopes closer to the perihelion, the reciprocal was true of post-perihelion measurements, where redder slopes are present in proximity to the Sun while bluer slopes slowly evolve with increasing heliocentric distance and decreasing activity. No major substructure was visible throughout this period, likely due to the viewing geometry, despite the presence of multiple known dust structures (Fans C through F). Spectral slopes within the central 3000 km on 11 January, 27 January, and 06 February were 18.2±2%/1000 ˚A, 10.2±1%/1000 ˚A, and 8.3±1%/1000 ˚A, respectively.
3.3. Gas Environment and Species Heritage Mentioned in Section 1, the molecules we observe in our gas maps are not primary products directly sublimated from the nucleus, but rather are secondary, tertiary, or even higher-order products resulting from photochemical, collisional, or thermal degradation processes in the coma. Tracing the formational heritage of these molecules is non-trivial, however, insights can be gained through comparing specific line ratios and employing idealised coma models. In the following section, we present the ratio of green to red-doublet 28 forbidden oxygen [OI] emission lines to dissect the dominance of H2O vs CO2 in the coma over different heliocentric distances.