Experimental Constraints on Evaporation Processes at Meridiani Planum

Introduction: In-depth analysis of evaporitic sediments at Meridiani Planum by the Opportunity Rover has highlighted the importance of fluid evaporation at the martian surface [1]. Previous work aimed at understanding the controls on evaporation and the resulting mineral assemblages has been largely theoretical [2]. Some recent experimental work has focused on evaporite minerals at the martian surface but has described only the resulting bulk mineralogy produced from fluid evaporation [3,4]. In order to more adequately understand the controls on saline mineral formation and resulting brine compositions, it is imperative that both solution and solid be characterized during the evaporation process itself. Here, we report on the experimental evaporation of synthetic basaltic weathering derived fluids. Complete solution and solid analyses throughout the evaporation process provide a wealth of data that are critical for: (1) understanding kinetic controls and complications that may be present in such geochemical systems and (2) updating and improving future theoretical modeling efforts to provide a more realistic interpretation of the processes involved in saline mineral production at the martian surface [5]. Methods and Analyses: The goal of the experiments is to fully characterize chemical changes in the evaporating fluid as well as precipitates produced over the course of the experiment. This is accomplished using the apparatus shown in Fig. 1, which consists of a 5L jacketed borosilicate reaction vessel. The entire vessel is vacuum-sealed via a 5-neck lid. A vacuum is maintained on the apparatus at a