Panel a: spatial distribution of dust optical depth at 9.3 μm (Montabone et al. 2020) averaged between L_s = 107.5–117.5° over a map of Mars. We also show the tangent point locations of ACS MIR solar occultations. We highlight occultations made using position 11, those in which HCl was observed, and those with coincident TIRVIM observation (northern only). Panel b: vertical profiles of HCl VMR from ACS MIR and dustmass loading from ACS TIRVIM (Luginin et al. 2020) for the coincident observation at (46°N, 97°W).