This graph shows a new CO2 spectral feature, never before observed in the laboratory, discovered in the martian atmosphere by the Atmospheric Chemistry Suite (ACS) MIR instrument on ESA's ExoMars Trace Gas Orbiter (TGO).
The graph shows the full extent of the magnetic dipole absorption band of the 16O12C16O molecule (one of the various 'isotopologues' of CO2).
The top panel shows the ACS MIR spectra (shown in black) along with the modelled contribution of CO2 and H2O (shown in blue); the model is based on the HITRAN 2016 database.
The bottom panel shows the difference between data and model, or residuals, revealing the structure of the absorption band in detail. The calculated positions of spectral lines are marked with arrows, in different colours corresponding to different 'branches' of the absorption band (red stands for the P-branch, green for the Q-branch and blue for the R-branch).
More information: ExoMars finds new gas signatures in the martian atmosphere