Abstract Extra-lunar contamination, fumarolic activity, and exposure to oxidizing gases from comet or carbonaceous meteorite impacts have been previously proposed as the causes of magnetite, hematite, and goethite in lunar materials. However, these minerals can occur in the stable low temperature gas-solid equilibrium assemblages of lunar rocks. Below 600°C magnetite is in equilibrium with C-O-H gases with compositions compatible with high temperature equilibrium with metallic iron; below 150°C hematite is stable in these same gases. Goethite is not stable in carbonaceous gases at low total pressure, and thus gases from impacting carbonaceous material cannot have produced it. Goethite is stable at low temperatures and pressures in almost pure H 2-H 2O gases. Its minimum stability against hematite is 2 bars total pressure at 130°C and 10 −3 bars at 30°C for H 2 to H 2O ratios compatible with the high temperature redox state of lunar materials. Thus the traces of magnetite, hematite and goethite in lunar materials may be the result of normal low-temperature processes indigenous to the Moon and not special processes.