From regolith to dirt: the role of organic matter in creating a fertile soil beyond Earth

The sustainability of space farming will rely on the exploitation of native regolith as a primary plant growth medium. However, extraterrestrial regolith differs fundamentally from fertile terrestrial soils because it lacks organic matter, some essential nutrients, and microbial communities. Moreover, its generally non-optimal pH significantly limits nutrient bioavailability and, consequently, crop growth. This perspective paper discusses sustainable strategies for transforming poorly fertile regolith into a life-sustaining substrate capable of providing ecosystem services and supporting space food production. Particular attention is given to the interactions between regolith minerals and exogenous organic matter as a key pathway for developing soil functionality beyond Earth.