Abstract DGP2026-12

Global Dust Storms (GDSs) on Mars are an impressive weather phenomenon. They can encircle the entire planet and threaten missions at Mars, by depositing dust on solar panels. However, GDSs remain challenging to predict. They only occur every few Martian years and without any external forcing due to inter-annual variations of the solar irradiation at the relevant time scales, the understanding of mechanisms behind the formation and inter-annual variability of GDS occurrence remains fragmentary. Previous studies have investigated the possibility that dust is being redistributed at the surface of Mars in a cyclic manner, in order to tentatively explain this inter-annual variability: Key dust reservoirs could be emptied during a GDS, and would take several years to be replenished, before the next GDS could occur. We use the Mars Planetary Climate Model (developed by the Laboratoire de Météorologie Dynamique in Paris, France) to model the dust redistribution at the surface of Mars and show that the redistribution patterns rather exhibit a low inter-annual variability. We therefore do not find evidence for such a cyclic behaviour of surface dust redistribution on Mars, explaining the inter-annual variability of GDSs. We further develop a new hypothesis based on saltation theory and the geographical heterogeneity of regolith particle sizes at the surface of Mars. First results using a simplified modelling approach show that this new hypothesis could be promising: We find that a relatively high threshold for dust emission in regions highly covered with dust, together with a natural, stochastic, inter-annual variability of surface winds, could be a key factor governing the inter-annual variability of GDSs.