0; Poch et al., 2020). One trend in our maps is the detection of CN signal solely from the southern hemisphere of 67P. Opitom et al. (2017) first reported the emergence of southern CN signal after the vernal equinox, likely caused by the change of season and migration of the subsolar point to the southern hemisphere of 67P. Similarly, observations by Knight et al. (2017) from 2015 report broad CN fans from the southern hemisphere, which further confirmed this trend. This 39 change in seasons illuminated long-dormant (5.5 yr)

reservoirs in the South, which intensely sublimated and both exposed new volatile-rich substrate and lofted larger dust particles. Intriguingly, this clear dependence was not detected from in-situ ROSINA measurements, which suggests the presence of an extended CN source that breaks down at distances further than several hundred kilometres from 67P. However, VIRTIS and ROSINA measurements highlight that the hemispherical difference in CN is not a product of 67P’s formation, but is rather a result of de-volatilisation across successive 5.5 yr northern summers (Bockel´ee-Morvan et al., 2016; Fougere et al., 2016). We observe this strong seasonal dependence and southern enrichment of CN post-equinox (6 August 2021), and find evidence for a correlation between the dust Fan B and a highly collimated CN jet (both originating from southern mid-latitudes). While we do eliminate the possibility of dust contamination in our CN maps (see Appendix Appendix B), we were unable to retrieve satisfactory fits for parent species scale lengths, thus limiting our interpretation of possible extended CN sources. Nonetheless, the strong correlation of dust Fan B and the pre-perihelion CN jet provides tentative evidence for the existence of CN distributed sources. This interpretation agrees with previous studies on possible extended sources of CN, e.g. in 1P/Halley (A’Hearn et al., 1986). We do see an enhancement in particle colour, and thus larger size or unique compositions, in the same region as the CN structure and dust Fan B from 31 August to 30 September. These larger red dust particles could similarly act as a transport mechanism for CN parent species, as we proposed for NH2 parent species. A possible scenario is that larger disintegrating dust particles, perhaps containing CHON particles or macromolecules within their porous interiors, could be a transport and source mechanism for the observed CN jet, rather than simply CHON particles or HCN nucleus outgassing alone. It should be noted that other parent molecules have been identified sublimating from southern mid-latitudes, such as HCN (L¨auter et al., 2022), which suggests both extended sources and traditional nucleic sublimation as sources for this CN structure and CN in the southern hemisphere. Extensive studies of nucleus and coma colour were conducted throughout the Rosetta campaign (Fornasier et al., 2015; Ciarniello et al., 2016; Filacchione et al., 2016; Fornasier et al., 2016), in which a strong orbital and seasonal dependences were found. These studies target different wavelength ranges from ∼4000 to 10000 ˚A, ground-based and in-situ. Nonetheless, the general trends are best described in Filacchione et al. (2020), across two win40 dows from 4000 to 5000 ˚A and 5000 to 8000 ˚A.