Black lines: normalized disk-integrated spectra of Mars between 1233.6 and 1234.5 cm⁻¹, recorded on July 6, 10, 11, and 14, 2018, shifted vertically by 0.0, −0.1, −0.2, and −0.3, respectively. In the July 6 spectrum, a spike was present at 1233.93 cm⁻¹, at the position of the CO₂ line, and has been removed. Red line: synthetic model, calculated using the atmospheric parameters described in Sect. 3.1, with H₂O₂ = 60 ppbv, shifted by −0.5. The spectral resolution of the models is 0.014 cm⁻¹.