In Ceres dwarf planet, a portion of a prior ocean at shallow depth may still exist today as localized reservoirs. In this work, we constrained chemical and geophysical properties of initial aqueous fluids, characterizing the reservoirs, located under two selected craters: Kupalo and Juling. At first, we applied FREZCHEM code to simulate brines’ freezing processes, under different values of initial total pressure in which the starting solutions have cooled to precipitate the solids characterizing these craters. Then, we compared the results with our chemical equilibria calculations to understand the equilibrium state for each precipitated mineral, during the cooling process, related to the activities of solutes and the ionic strength of solutions. Decreasing temperature caused the precipitations of carbonates (thermodynamically favored), followed by the formation of sulphates and, later, of Cl-bearing salts from more saline brines. Solids precipitation feeds cooling process, changing the velocity/density ratios of aqueous solutions that would have arrived at surface erupting with a velocity of ⁓8·10-5 m/s. An excess of pressure in the reservoirs could have supported an intrusion of briny materials to surface, and, in our simulations, we suggest that sodium-salts formation is pressure-dependent. This supports the hypothesis that different “cooling chambers”, at different pressure conditions, may exist under the craters. Moreover, beneath Kupalo, at specific pressure condition, some kinetics-dependent molecules could form, suggesting that aqueous solutions plausibly were affected by kinetics slower than the nearby Juling.
