Understanding Phosphorus Dynamics in Martian and Lunar Regolith Simulants: Insights for Space Agriculture

Phosphorus (P) is a vital nutrient for plant growth and development, making it essential for sustaining agriculture as human colonies are established in space. However, there is limited knowledge of native P forms and of the interaction between applied P and the lunar or Martian regolith. This highlights the need to examine how this essential nutrient interacts with the regolith for sustainable P management. In this study, we completed P adsorption experiments, followed by desorption experiments, to assess P retention and release in lunar and Martian regolith simulants. Additionally, Hedley sequential extraction was used to characterize the P pools in the simulants before and after the adsorption experiments. Results showed that lunar simulants exhibited limited P adsorption and retention across a range of pH values; in contrast, Martian regolith demonstrated high P adsorption and retention. After application of P, Martian regolith simulants released varying amounts of P back into the solution during desorption experiments. Hedley sequential extraction revealed that most native P was stored in pools inaccessible for the plant uptake. Furthermore, the results indicate that Al- and Fe-bound minerals are likely the primary controlling minerals for P adsorption and retention in Martian simulants. Overall, this study lays the foundation for understanding P chemistry in lunar and Martian simulant regolith and supporting the development of P management strategies for extraterrestrial agriculture.