Characterization Of Perchlorate Photostability Under Simulated Martian Conditions

Abstract

During the NASA Mars Phoenix Mission, high levels of perchlorate were detected in test soils using the Wet Chemical Laboratory (WCL), a component of the Microscopy, Electrochemistry and Conductivity Analyzer (MECA) instrument suite (Hecht et al. 2009). At Mars temperatures, perchlorate alone should not adversely affect the potential habitability of martian soil. However, the presence of perchlorate suggests that other more reactive oxychlorine compounds, which could not be measured by the WCL (e.g., hypochlorite, which is commonly known as chlorine bleach), may also be present. If present, these reactive species may have significant impacts on habitability and the alteration of possible organic biosignatures on Mars. Using an environmental chamber located at NASA Ames Research Center, we are investigating the photostability of magnesium and calcium perchlorate under Mars-like conditions. Potential perchlorate decomposition and the formation of reactive oxychlorine species are being characterized as a function of UV flux, oxygen availability, temperature, humidity, and catalytic activity, during experiments carried out in a 10 mbar simulated martian atmosphere. We will report on perchlorate decomposition and lower oxidation state oxychlorine (e.g., hypochlorite) formation rates measured using UV spectroscopy. Potential relationships between perchlorate stability and soil habitability on Mars will also be discussed.