We show that the long-standing discrepancy between observed and calculated spectra of the PFS/MEx in the cores and wings of 4.3-micron region is explained by the non-thermal rotational distribution of molecules in the upper vibrational states of second hot (SH) CO₂ bands above 90 km altitude. We discuss the implications that accounting for this effect has for developing operational algorithms aimed at massive processing of PFS and other instrument limb observations.