Perchlorates on Mars: Implications for the Detection of Organics on Mars

Abstract

In 1976, the Viking Mars Landers analyzed surface samples for the presence of organic compounds using gas chromatography-mass spectroscopy (GC-MS). On Mars, trace levels of organics, including chloromethane and dichloromethane, where detected. However, these species were attributed to preflight system contamination (Biemann et al. 1976). In 2008, perchlorate was detected in Martian soil using the Thermal and Evolved-Gas Analyzer and Wet Chemical Laboratory on the NASA Mars Phoenix Lander (Hecht et al. 2009). This has prompted the reinvestigation of the source of the halogenated hydrocarbons detected by the Viking GC-MS. Recent work has concluded that the origin of the chloromethanes in the Viking GC-MS results was the reaction of perchlorates and Martian soil organics during sample heating in the GC-MS analyses (Navarro-Gonzales et al. 2010). This has prompted the investigation of alternative mechanisms for the formation of chloromethanes in the Viking GC-MS experiments that do not involve the presence of soil organics including, the reaction of perchlorates with terrestrial organic contamination and Fischer-Tropsch type synthesis. By conducting simulations identical to the GC-MS experiments performed on the Viking Landers, we seek to resolve the debate on whether or not Viking soils contained detectable levels of organic compounds.