Abstract We present a nine‐Martian‐year survey (MY 28–MY 36) of solar occultation measurements taken by the SPICAM IR spectrometer on Mars Express to chart the seasonal and spatial variations of dust and water ice in the atmosphere. Total aerosol extinction profiles demonstrate significant seasonal variations, reaching up to 80 km during perihelion and 40 km during aphelion. However, from profiles in the 1–1.7 μm range, we cannot distinguish between dust and water ice. We attribute these two types of aerosols in SPICAM profiles using Mars Climate Sounder (MCS) data from the Mars Reconnaissance Orbiter, water vapor data from SPICAM, and general circulation model (GCM) predictions. We validate the attribution against simultaneous aerosol measurements from the Atmospheric Chemistry Suite on the Trace Gas Orbiter. The retrieved effective radius of dust ranges from 0.3 to 1 μm and the number density ranges from ≤0.1 to 10 cm −3 , slightly depending on seasons. The effective radius of water ice varies from 0.1 to 3 μm with a number density ranging from 0.1 to 100 cm −3 . High‐altitude mesospheric clouds were detected at 70–90 km during global and regional dust events. Polar hood clouds were characterized by an optical depth above 0.1, small particle sizes (0.2–1.2 μm in effective radius), and a number density greater than 5 cm −3 . SPICAM's mass mixing ratio of both water ice and dust is consistent with MCS and GCM values, except during perihelion and C‐storm occurrences, when the model underestimates them.
Fedorova et al. (Sun,) studied this question.