Raman Spectroscopy Applied to Mars Water Cycle Studies

One of the key findings during the Phoenix and Mars Science Laboratory landed Mars missions has been the detection of perchlorate, a highly deliquescent salt. Perchlorates are of great interest on Mars due to their high affinity for water vapour as well as their ability to greatly depress the freezing point of water when in solution. This has intriguing biological implications as resulting brines could potentially provide a habitable environment for living organisms. Additionally, it has been speculated that these salts may play a significant role in influencing the hydrological cycle on Mars. In order to experimentally study brine formation on Mars and assess the feasibility of a future landed detection tool, a stand-off Raman spectroscopy instrument and environmental simulation chamber have been developed at York University. A sample of magnesium perchlorate has been subjected to the water vapour pressure, background pressure and temperatures found at polar Martian latitudes. Results indicate that at a water vapour pressure of ~20 Pa, Raman spectroscopy is able to detect the onset of brine formation and provide an estimate of the quantity of water taken up by the sample. At the lower water vapour pressures typically found on Mars ( ~1 Pa), it appears that slower dynamics inhibit the onset of water uptake over relevant time scales. The experimental setup and current results will be presented.