User:Alec Fitting/Water on Mars

Present Water
It is possible that liquid water could also exist on the surface of Mars through the formation of brines suggested by the abundance of hydrated salts. Brines are significant on Mars because they can stabilize liquid water at lower temperatures than pure water on its own. Pure liquid water is unstable on the surface of the planet, as it is subjected to freezing, evaporation, and boiling. Similar to how we salt roads on Earth to prevent them from icing over, briny mixtures of water and salt on Mars may have low enough freezing points to lead to stable liquid at the surface. Given the complex nature of the Martian regolith, mixtures of salts are known to change the stability of brines. Modeling the deliquescence of salt mixtures can be used to test for brine stability and can help us determine if liquid brines are present on the surface of Mars. The composition of the Martian regolith, determined by the Phoenix lander, can be used to constrain these models and give an accurate representation of how brines may actually form on the planet. Results of these models give water activity values for various salts at different temperatures, where the lower the water activity, the more stable the brine. At temperatures between 208 K and 253 K, chlorate salts exhibit the lowest water activity values, and below 208 K chloride salts exhibit the lowest values. Results of modeling show that the aforementioned complex mixtures of salts do not significantly increase the stability of brines, indicating that brines may not be a significant source of liquid water at the surface of Mars.