Ground-based observations provide critical context for understanding the chemical and physical evolution of the coma. Recent radio, infrared, and optical studies by Biver et al. (2023), Bonev et al. (2023), Boehnhardt et al. (2024), and Ivanova et al. (in prep.) examined the dust and gas environment of 67P during its 2021 apparition, both pre- and post-perihelion. Notably, the studies identified dust structures that align closely with the temporal and angular ranges of multiple structures and fans observed in our dataset. Boehnhardt et al. (2024) utilised Laplacian filtering techniques to detect several fans, neck-line features, and streamer structures across 33 epochs spanning 21 May 2021 to 1 June 2022, which best complements our dataset. Their work revealed four dynamically modelled dust fans located at latitudes of +40◦N and –10◦S pre-perihelion, and –10◦S, –50◦S, and –70◦S post-perihelion. The post-perihelion fans at –10◦S, –50◦S, and –70◦S correspond to active regions previously identified by Boehnhardt et al. (2016) and recently modelled using ROSINA measurements by L¨auter et al. (2022). Further works from the 2015 apparition also report dust structures similar to our own (Knight et al., 2017). Our Fans B through F show a coarse correlation with their reported –10◦S, –50◦S, and –70◦S active regions. It should be noted that pre-perihelion Fan B is likely just post-perihelion Fans C through F superimposed onto each other due to the side-on viewing geometry pre-perihelion. Biver et al. (2023), Bonev et al. (2023), and Ivanova et al. (in prep.) report finding similar dust fans across the apparition, and corroborate these findings with an active region around –58◦±5◦S. We find similar structures in 2016 MUSE observations, seen in Figure 12, that fur35 ther supports long-term stability of these dust features and activity sources over multiple apparitions.

Lower latitude emission sources and structures were present (purple and orange lines, -10◦to -30◦S, -40◦to -50◦S), however, the highest latitude structures are not seen. This is most likely due to the 4× larger FoV in the 2016 MUSE data, and significantly higher heliocentric and geocentric distances of 2.5 and 1.5 au, respectively. In situ measurements by MIRO in 2015 (Biver et al., 2019) detected elongations of various parent molecules (NH3, CH3OH, CO) and water isotopologues (H16 2 O, H17 2 O, H18 2 O) originating from ϕ = -80◦±5◦S, with a fan width of 100◦–130◦
around perihelion. This provides further evidence for the stability of active regions across multiple apparitions, tenuously links the Rosetta and Earthbased observational scales, and aligns well with the lowest latitude reported by Boehnhardt et al. (2024) and our study. These findings also agree with our reported widths, position angles, and proposed southern activity sources for dust Fans C-F, and molecular structures of C2, NH2, [OI], and CN, as detailed in Subsections 3.1.1 and 3.1.2.

[Figure: Figure 12: Comparison of post-perihelion fans from 2022 (top panel) and 2016 (bottom panel). The red, lime, yellow, and white arrows are the same annotations as Figures 3 through 8. The concentric rings denote cometocentric distance, in units of kilometres. The purple dashed line corresponds to active region between -10◦to -30◦S. The orange dashed line corresponds to -40◦to -50◦S. The yellow dashed line corresponds to -60◦to -80◦S. The cyan line is the South Pole of 67P. Binning is 1×1.]