Abstract
Perchlorate (ClO4−) is globally enriched in Martian regolith at levels commonly toxic to plants. Consequently, perchlorate in Martian regolith presents an obstacle to developing agriculture on Mars. Here, we assess the effect of perchlorate at different concentrations on plant growth and germination, as well as metal release in a simulated Gusev Crater regolith and generic potting soil. The presence of perchlorate was uniformly detrimental to plant growth regardless of growing medium. Plants in potting soil were able to germinate in 1 wt.% perchlorate; however, these plants showed restricted growth and decreased leaf area and biomass. Some plants were able to germinate in regolith simulant without perchlorate; however, they showed reduced growth. In Martian regolith simulant, the presence of perchlorate prevented germination across all plant treatments. Soil column flow-through experiments of perchlorate-containing Martian regolith simulant and potting soil were unable to completely remove perchlorate despite its high solubility. Additionally, perchlorate present in the simulant increased metal/phosphorous release, which may also affect plant growth and biochemistry. Our results support that perchlorate may modify metal availability to such an extent that, even with the successful removal of perchlorate, Martian regolith may continue to be toxic to plant life. Overall, our study demonstrates that the presence of perchlorate in Martian regolith provides a significant challenge in its use as an agricultural substrate and that further steps, such as restricted metal availability and nutrient enrichment, are necessary to make it a viable growing substrate.
Highlights
Human habitation of Mars will have to prioritize and optimize shipments to provide resources for life, inclusive of food, water, and shelter
Of the two plant species, only Phaseolus vulgaris was able to germinate in Martian regolith simulant, and only without added perchlorate (Figure 1)
Seed germination data were analyzed across all trials by using a germination rate index (GRI) as a composite of both germination rate and percentage of seeds (Figure 2A)
Summary
Human habitation of Mars will have to prioritize and optimize shipments to provide resources for life, inclusive of food, water, and shelter. As no life has been identified on Mars, plant seeds will need to be transported from Earth for food production. One practical way to solve this agricultural problem is to utilize Martian regolith, as it is derived from rocks similar to those on Earth. Using Martian regolith would allow increased agricultural expansion in environmentally controlled spaces such as prebuilt structures or sealed/modified lava tubes [1,2,3]. Despite the potential of Martian regolith as a growing medium, Mars’ planetary history has created toxic conditions that need to be addressed if food production is going to be successful
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