The Mars Aqueous Processing System (MAPS) is a novel technology for recovering oxygen, iron, and other constituents from lunar and Mars soils. The closed-loop process selectively extracts and then recovers constituents from soils using acids and bases. The emphasis on Mars is production of useful materials such as iron, silica, alumina, magnesia, and concrete with recovery of oxygen as a byproduct. On the Moon, similar chemistry is applied with emphasis on oxygen production. Most lunar LOx processes only reduce FeO, which is generally present at just 10 to 15 percent in soils. All of the soil must be heated to reduce the contained FeO, resulting in substantial heat transfer issues. Thermal power requirements per unit of oxygen recovered are reduced by an order of magnitude and hydrogen losses are minimized if only a small mass of high-grade iron oxide concentrate, such as that produced by MAPS, is subjected to hydrogen reduction. MAPS is significant because it can be co-developed for Mars and Moon applications. The process would be commissioned first for oxygen production on the Moon. Modular enhancements for manufacture of additional products would be implemented on the Moon and then on Mars, thereby reducing risks and costs.