Understanding Martian Salts and Their Implications for Liquid Water

Water is one of the key components for life as we know it. The existence of salts on Mars has been a large contributing factor to the possibility of habitability, due to their ability to allow liquid water to remain stable at colder temperatures. Salts, including perchlorates, chlorates, and chlorides, have been detected by multiple landers, rovers, and orbiters, and are now believed to be ubiquitous on Mars. One of the pathways to liquid brine solutions is through deliquescence. Deliquescence is the transition from a solid salt crystal into an aqueous solution when exposed to a humid atmosphere. This research explores the deliquescence process in a laboratory setting, field site in the Atacama Desert, and through modeling. The first half of this work focused on experiments conducted in the Ares Mars simulation chamber at the Keck Lab at the University of Arkansas. Calcium perchlorate mixed with JSC Mars-1 with ~20% relative humidity and temperatures ranging from 274- 278 K were tested to see if deliquescence can occur under those conditions and if so, does regolith darkening occur. Part two of the experiments focused on expanding the Mars simulation chamber’s protocol to allow higher humidity in the chamber. Deliquescence/efflorescence cycling was examined in the Atacama Desert, when multiple pure salts and a sample of calcium perchlorate mixed with Atacama soil were exposed to desert conditions over seven months. Electric conductivity, relative humidity, and temperature were recorded to verify if the cycling had occurred. Finally, ternary mixtures of chloride, chlorate, and perchlorate with either calcium or magnesium were modeled at temperatures from 273-223 K to determine what salts would provide the most stability for a briny solution in Mars-like conditions. The evaporation model ascertained the deliquescence relative humidity and eutonic humidity point and their corresponding salt mixtures