Perchlorate on Mars: Risk and Resource

The ubiquitous presence of magnesium and calcium perchlorate in the Mars regolith is a challenge for human exploration (perchlorate is toxic)[1], but it's also an opportunity for in situ resource utilization. We propose to create a Mars life-support loop that will (1) remove perchlorate from simulated Mars regolith and (2) use astronauts to provide microbes for functional enzymes (ureases) to convert urea in urine into ammonia; and (3) recover ammonia from urine as ammonium to be available for making ammonium perchlorate--a major component of rocket fuel. TECHNICAL IMPLEMENTATION Perchlorate, abundant on Mars (0.5-1.0 wt% of regolith), is a severe health hazard for Mars explorers. Inhaled or ingested perchlorate from Martian dust or drinking water competitively inhibits the uptake of iodine by the thyroid, which impacts essential hormones. While perchlorate is a health risk, it is also a potential resource for both the production of oxygen and rocket fuel (Davila et al., 2013). To apply this observation to Mars, simulated Mars regolith will be extracted to detoxify and recover perchlorate that can be used to make fuel by combining it with ammonium recovered from human urine. Humans typically urinate 1.2 liters per day and may sweat 0.5- 4.0 liters per day, depending on activity. Urine contains urea that was enzymatically transformed into ammonia using the enzyme urease obtained from microbes recovered from urine. The ammonia was captured in an acid trap as ammonium, which can be combined with extracted perchlorate to synthesize ammonium perchlorate, which is combined with aluminum and binders to make rocket fuel. We estimated that more than 10 Kg of perchlorate can be extracted from 1m3 of Martian regolith, but the ammonium available from human Mars explorers will be limiting. See uploaded file. More »