In this work, we utilised MUSE observations of comet 67P/Churyumov-Gerasimenko to generate simultaneous maps of dust, C2, NH2, [OI], and CN comae across 12 observational epochs pre- and post-perihelion. These maps were employed to investigate the evolution and composition of 67P’s middle and outer coma during its most recent apparition, placing our findings within the broader context of Rosetta’s 2014-2016 results from the nucleus and inner coma environments. We did not carry out detailed modelling, as it is outside the scope of this paper. Our major findings are:
1. We deconstructed the gas-dust coma into constituent and concurrent maps of dust and gas species. We followed the morphological evolution of dust and gas species across the apparition, and found well-known dust fans and structures (Boehnhardt et al., 2016; Biver et al., 2023; Bonev et al., 2023; Boehnhardt et al., 2024; Ivanova et al., in prep.). We also found gas signal from C2, NH2, [OI], and CN, and noted the unique association of NH2 signal and CN signal with the aforementioned dust structures. Finally, our results build upon the accepted notion of longterm stability of active sources on 67P, across multiple apparitions. 2. In the gas maps, we identified two pre-perihelion evolutionary regimes: (1) evolving H2O ([OI]1D) and C2 signal, (2) stable NH2, dust, and CN signal. We present arguments, in the context of other Earth-based and in-situ Rosetta studies, that different production processes are responsible for the two regimes. We propose that the (1) evolving regime is linked to sublimation directly from the nucleus and subsolar evolution (both molecules), while the (2) stable regimes are the joint product of distributed coma sources (NH2, CN) and seasonal effects. 3. We investigated the connection of NH2 and CN to known dust structures, and probed their relation to emission from extended sources. We also find that the pre-perihelion northern NH2 structure has photochemical scale lengths 1.5-1.9× the rest of the coma, which suggests a mechanism that preserves the parent species until further from the nucleus, thus enhancing the effective scale length. We propose a possible extended source of ammoniated salts (Altwegg et al., 2020; Poch et al., 2020). Signal-to-noise restricted this similar analysis of CN and other species, however, we performed tests to ensure that the CN signal corresponding to Fan B was not contaminated by residual dust flux.

We did not find any dust flux, and confirmed the CN signal to be real. However, we do see larger, redder dust particles in our colour maps which correspond to both the CN and dust Fan B morphologies, which could explain why CN signal is found with the dust since parent species would be preserved in these larger dust particles for longer. Finally, in the context of Rosetta results which show an excess in CN signal that cannot be explained by HCN photolysis alone directly from the nucleus, we propose that CN is also produced in-part by extended sources in the south (e.g., H¨anni et al., 2020). However, we do note that NH2 and CN signal is likely to come from both traditional nucleus sublimation and these distributed sources (L¨auter et al., 2022). 4. We computed dust spectral slope maps, in which the spectral slope, or colour, of the dust could be quantified. Largely, we report evolutionary trends consistent with Rosetta findings (Filacchione et al., 2020). 5. We calculated the G/R [OI] ratio across perihelion to probe the H2O to CO2/CO dominance of the coma. We found G/R ratios were generally consistent with an average value of 0.1. This implies that the coma is dominated by water sublimation throughout our observational campaign.