BIOGEOCHEMISTRY OF PERCHLORATE IN MARTIAN REGOLITH

Martian regolith is enriched with perchlorate (ClO₄^-). As a result, humans may not be able to use martian regolith as a medium to grow plants. Here, we assessed plant growth (i.e., amaranth and bean) growing in potting soil and simulated martian regolith with varying concentrations of perchlorate. Prior to the experiments, we determined that perchlorate quickly volatilizes (i.e., 50 g of Mg perchlorate left exposed to the atmosphere sublimated completely in less than eight hours). Chlorine gas released from this process poses a problem in closed greenhouse environments. Based on our experiments, we observed that perchlorate, even at low concentrations, was detrimental to plant growth. Plants in potting soil were able to germinate in weight concentrations of 1 wt. % perchlorate; however, these plants were visibly stressed. During these experiments, watering the soil/plant was not able to completely remove all the perchlorate despite its high solubility. Plants in simulated martian regolith with no perchlorate all germinated; however, seeds failed to sprout in martian regolith when perchlorate was present. Overall, our study demonstrates that perchlorate, whether in martian regolith or soils on Earth, is detrimental to plant growth.