Sulfate Brine Stability Under a Simulated Martian Atmosphere Jackie D Denson, Vincent Chevrier, and Derek Sears

1. Sulfate Brine Stability Under a Simulated Martian Atmosphere Jackie D Denson, Vincent Chevrier, and Derek Sears W.M. Keck Laboratory for Space Simulation University of Arkansas Center for Space and Planetary Sciences, Fayetteville Arkansas Initial Results Background: Evidence for the presence of sulfate containing sediments on Mars dates as far back as the Viking era. (1) Recently the Omega hyperspectral imager on Mars Express has mapped extensive sulfate bearing minerals to km and sub-km resolution (Fig. 1 and 2). These observations have shown that MgSO4-minerals are a major component of the Martian regolith (Table 1). (2)These minerals have the ability to exist in a variety of configurations with different states of hydration,and could therefore play a significant role in our understanding of the state of water on Mars (Fig. 3). When compared to the evaporation rates predicted for pure water under the same conditions sulfate brines evaporate more slowly (Fig. 4-6). Based on our initial results this appears to be a multifactored process as subtle differences in temperature and humidity can lead to dramatic differences in evaporation rate (Fig. 4 vs Fig. 5).Experimental refinements are currently underway to develop better techniques of controlling the humidity of our simulated atmosphere. Crystal formation has also been observed in highly concentrated brines. This process of crystallization and hence the hydration state of the MgSO4 under various conditions will be examined by X Ray Diffraction. Table 1. Gendrin et al. (2005) Fig. 4 20% Wt MgSO4 with flowing CO2 Objectives: In order to better understand the stability of sulfate brines on Mars a series of experiments were performed to quantify the rate of evaporation of various brine concentrations under a simulated Martian atmosphere utilizing the Andromeda chamber. It was hypothesized that highly concentrated sulfate brines have the potential to retain a significant amount of H20 in the polyhydrated state. Fig. 5 20% Wt MgSO4 Fig. 1 Gendrin et al. (2005) Fig. 6 25% Wt MgSO4 Fig 3. Dalton et al. Methods: Experiments were performed in the Andromeda chamber, in a simulated Martian CO2 atmosphere with a constant pressure between 5 and 6 Torr, and temperature of 0°C. Brines were place in petri dishes along with a thermocouple and placed onto an analytical balance located within the chamber, Mass loss was measured for ~ 2 hrs for each experiment. Acknowledgements: I would like to thank Julie Chittenden, Kathryn Bryson, and Walter Graupner for their immense help in learning to operate the Andromeda chamber, and Dr. Sears and Dr. Chevrier for their help and guidance. • References: • Vaniman D, Bish D, et al. Nature (431)2004.. • 2. Gendrin A, Mangold, N, et al. Science,(307) 2005. • 3. Dalton J, et al. Icarus (177) 2005. Fig. 2 Gendrin et al. (2005)