Potassium ferrate [Fe(VI)] does not mediate self-sterilization of a surrogate mars soil

Under ambient conditions (25°C, oxygen and water present) K2FeO4 mixed into sand mineralized some reactive organic molecules to CO2, while less reactive compounds were not degraded. Dried endospores of Bacillus subtilis incubated in a Mars surrogate soil comprised of dry silica sand containing 20% by weight K2FeO4 and under conditions similar to those now on Mars (extreme desiccation, cold, and a CO2-dominated atmosphere) were resistant to killing by the ferrate-enriched sand. Similar results were observed with permanganate. Spores in oxidant-enriched sand exposed to high fluxes of UV light were protected from the sporocidal activity of the radiation below about 5 mm depths.Based on our data and previously published descriptions of ancient but dormant life forms on Earth, we suggest that if entities resembling bacterial endospores were produced at some point by life forms on Mars, they might still be present and viable, given appropriate germination conditions. Endospores delivered to Mars on spacecraft would possibly survive and potentially compromise life detection experiments.The results of life-detection experiments performed almost three decades ago on Mars by the Viking lander have long been subject to controversy [1-3]. Many scientists, though certainly not all [3,4], have concluded that results of Viking biological experiments can be interpreted as an indication of the presence of strong oxidants in the Martian soil [5-7], rather than biological activity. They suggest that these oxidants are capable of oxidizing organic materials causing release of carbon dioxide as seen in the Viking experiments. Since oxygen was also released after humidifying a sample of Martian soil, these proposed oxidants would also oxidize water. The spontaneous reduction of Ferrate(VI) in water forms molecular oxygen and Fe(III) [8]. The rate of this reaction is strongly pH dependent [9]. Other observations by Viking have complicated data interpretation, including the transient absor