Goals and objectives aqueous salt solutions are critical for understanding the potential for liquid water to form on ICY worlds and whether brines are suitable for life. Salty solutions can form…

This $466,261.99 grant was awarded by the National Aeronautics and Space Administration (NASA) Shared Services Center to the University of Washington to study the potential habitability of aqueous salt solutions on icy worlds like Mars, Europa, and Enceladus. The research aims to measure the thermodynamic properties of salt solutions at low temperatures and develop new models for understanding how water activity, brine composition, and crystalline salt assemblages relate to habitability and past environmental conditions on these planetary bodies. The grant does not have a set-aside designation. As a leading research university, the University of Washington has received numerous prime federal contract and grant awards across a range of scientific disciplines relevant to NASA's Habitable Worlds program.

Goals and objectives aqueous salt solutions are critical for understanding the potential for liquid water to form on ICY worlds and whether brines are suitable for life. Salty solutions can form potentially habitable environments by depressing the freezing point of water down to temperatures typical of mars surface or the interiors of europa or enceladus. Furthermore, crystalline salts are sensitive indicators of the processes by which they formed, such as freezing or evaporation, and environmental conditions such as PH, temperature, pressure, and salinity. The study of aqueous solutions and salt assemblages on ICY worlds requires an understanding of the low-temperature properties of salt solutions and the different conditions under which crystalline salts form. Currently, experimental data on low temperature salt systems are generally lacking, which makes IT impossible to develop accurate models that can be used to study salt solutions as a function of temperature and pressure. To address these issues, we propose to: 1. Measure thermodynamic properties in simple salt solutions and salt mixtures, including solubilities, water and ION activities, heat capacities, and solution enthalpies and 2. Build new, low-temperature thermodynamic models using this data, with applications towards studying aqueous solutions and soluble salt assemblages on ICY worlds. The aqueous models that we develop will be a significant improvement over current low-temperature model, which can be grossly in error when extrapolated into experimentally unexplored regions, and do not include important chemical species relevant to biology, such as chlorates and some nitrates. Our goal is to evaluate the potential habitability of low-temperature brines and what crystalline salt assemblages tell US about environmental conditions. This will address fundamental questions about habitability, including 1. How does water activity change as a function of salinity and temperature and does IT remain at habitable levels. 2. HAT brine compositions form on planetary surfaces under different evaporative or freezing scenarios. 3. What do salts tell US about past environmental conditions. We will determine the thermodynamic properties of chloride, chlorate, perchlorate, sulfate, nitrate, and ammonium ammonia solutions, as well as mixtures of these salts, from 150 to 300 k. Water activities, heat capacities, and solution enthalpies will be determined using the isopiestic method, differential scanning calorimetry, and isothermal titration calorimetry respectively. Equilibrium and dynamic phase transitions will be measured using an aqueous cryogenic reaction vessel and by DSC. These experimental results will then be used to build comprehensive, internally consistent equilibrium models for salt solutions, which we will apply to understanding aqueous solutions on mars, europa, and enceladus. This research addresses fundamental questions about the habitability and past aqueous history of mars and the ICY moons europa and enceladus. The models that will be developed are useful for interpreting current identifications of soluble mineral assemblages in terms of past aqueous environmental conditions, and for guiding future exploration into soluble mineralogy on mars and other ICY worlds. This research is relevant to the habitable worlds program focus on the presence of water and or exotic solvents and water body physics and chemistry as they pertain to habitability and habitability over time. The data that will be gathered and the models that will be developed and made available open source address a critical area of experimental research that clearly has missing data, and is relevant to the astrobiological potential of past or present environments on or in the martian surface or subsurface and the astrobiological potential of ICY worlds in the outer solar system, particularly europa and enceladus.