Summary

The atmosphere of Mars, like most planetary atmospheres, consists of molecules absorbing and emitting in the infrared (IR) and of particles (dust or clouds) that also interact with the IR radiation. This makes the IR spectral range highly effective for the study of the atmospheric composition and thermal structure. Since the first missions to Mars, infrared spectrometers have been used to study the atmosphere. Thermal IR instruments, which sense the emission from the surface and the atmosphere of Mars, as well as near-IR spectrometers, sensitive to the reflected solar radiation, deliver the three-dimensional structure of the atmosphere and permit monitoring of the CO₂, H₂O, CO, and aerosol cycles over Mars’s seasons. IR spectroscopy at high spectral resolution from the ground or from orbit is the most commonly used method to search for unknown species and to monitor the known minor components of the Martian atmosphere. It is also used to study isotopic ratios essential for understanding the volatile evolution on the planet.