Constraints on the distribution of CaSO4·nH2O phases on Mars and implications for their contribution to the hydrological cycle

► Gypsum is resistant to dehydration on Mars due to low temperatures. ► Gypsum dehydration is limited to local areas which experienced high temperatures. ► Anhydrite remains stable below 1%RH. ► Bassanite is the expected dehydration product. ► Bassanite is likely restricted to mid and low latitudes.