Can cold atmospheric plasma make water enriched with minerals from Martian or Lunar regolith more suitable for hydroponic plant growth?

In space agriculture, a soil-free cultivation method with low system complexity and mass, hydroponics offers passive aeration, automation, and a means to overcome inefficient distribution of water and limited convective mixing of substrate-based growth systems under micro- and low gravity conditions. Incorporation of local regolith into the hydroponics system has been considered as a step towards in situ resource utilisation, however previous studies demonstrated reduced growth and stress morphologies in plants grown in regolith. This study explores whether cold atmospheric plasma (CAP) treatment can be used to improve the quality of water enriched with regolith particles, and thus enhance the growth, yield and vitality of microgreens. CAP treatment of Simulated Martian Regolith (W-SMR) water for 10 or 30 min increased shoot length of Brassica oleracea by 114% and 89%, and Medicago sativa by 218% and 195%, respectively. For Simulated Lunar Regolith (W-SLR), CAP treatment increased shoot length of M. sativa by 113% and 88%, and B. oleracea by 108% and 129%. Root length also increased, notably for M. sativa in W-SLR and B. oleracea in W-SMR, with smaller effects for M. sativa in W-SMR. CAP treatment was found to alter the concentration of essential elements known to affect plant development, increasing the concentrations of ²⁴Mg, ³¹P, ³⁹K, ⁶⁶Zn, and ⁴⁴Ca known to promote plant growth, while reducing the concentrations of ⁵¹V and ²⁷Al that may be responsible for a greater level of stress in plants grown in untreated solutions due to their influence on enzymatic processes. These results confirm the potential of CAP treatment to improve productivity of hydroponic systems that utilise local regolith as an alternative to closed loop systems.