SPICAM-IR, an AOTF spectrometer onboard Mars Express spacecraft with a resolving power of 2,000 covering the spectral range 1-1.7 μm has been observing Mars since 2004. In this wavelength range, it is possible to distinguish between CO2 and H2O ices and measure their band depths. We obtained about 200,000 high-fidelity spectra of CO2 ice in different seasons and locations over the Martian polar caps. The spectra have been associated with slab ice, fine-grained ice, permanent caps, and dark and dirty ice at the cryptic region of the south polar cap. Also, we observed more than 200,000 water ice spectra, specifically its broad feature around 1.5 μm. Water ice is present at the surface or in the atmosphere resulting in a variety of different band depths, often in combination with the CO2 ice. We mapped the equivalent width of 1.43 μm CO2 ice band and the depth of 1.5 μm water ice band, which are the proxies for grain size, and followed their seasonal evolution. From the maps, we produced the edge (outer crocus line) of the CO2 south and north caps for nine Martian Years. The cap edges evolve similarly through all years and are in good agreement with previous OMEGA/Mars Express observations. We also discuss the impact of the global dust storms on the cap edges. Lastly, we interpret some of the water ice observations as water ice clouds in the aphelion cloud belt and the polar hoods.

Carbon monoxide is a non-condensable species of the Martian atmosphere produced by the photolysis of CO2. Its mixing ratio responds to the condensation and sublimation of CO2; from the polar caps, resulting in seasonal variations of the CO abundance. Since 2018, all three spectrometers of the Atmospheric Chemistry Suite (ACS) onboard the Trace Gas Orbiter have measured CO in infrared bands by solar occultation. Here we provide the first long-term monitoring of the CO vertical distribution at the altitude range from 0 to 80 km for 1.5 Martian years from Ls=163; of MY34 to the end of MY35. We obtained a mean CO volume mixing ratio of ~960 ppm at latitudes from 45S to 45N, mostly consistent with previous observations. We found a strong enrichment of CO near the surface at Ls=100-200; in high southern latitudes with a layer of 3000-4000 ppmv, corresponding to local depletion of CO2. At equinoxes we found an increase of mixing ratio above 50 km to 3000–4000 ppmv explained by the downwelling flux of the Hadley circulation on Mars, which drags the CO enriched air. The general circulation chemical model tends to overestimate the intensity of this process, bringing too much CO. The observed minimum of CO in the high and mid-latitudes southern summer atmosphere amounts to 700-750 ppmv, agreeing with nadir measurements. During the global dust storm of MY34, when the H2O abundance peaks, we see less CO than during the calm MY35, suggesting an impact of HOx chemistry on the CO abundance.