Iron(VI): Hypothetical Candidate for the Martian Oxidant

As a result of the Viking missions of the early 1970s, the presence of a strong oxidant in martian soil was suggested. Here we present a hypothesis, testable by near-term missions, that iron(VI) is a likely contributor to the martian oxidative pool. In this context, ferrate(VI) salts, with FeO 4 2− anion, were studied for their spectral and oxidative properties. Ferrate(VI) has distinctive spectroscopic features that make it available for detection by remote sensing reflectance spectra and contact measurements via Mössbauer spectroscopy, and the relevant miniaturized instrumentation has been developed or is under way, while for the returned samples XANES spectroscopy is shown to be a method of choice. Ferrate(VI) is capable of splitting water to yield molecular oxygen, and oxidizing organic carbon into CO 2. These activities were strongly abated after treatment at elevated temperatures, similar to observations with martian soil samples in the Viking mission.