Early missions to Mars such as Robert Zubrin’s Mars Direct architecture will require propellant production for the trip home. Methane can be produced in situ on the red planet’s surface through the basic chemical reaction CO2 + 4H2 → CH4 + 2H2O. A French chemist named Paul Sabatier discovered back in 1897 that this reaction could be facilitated by a nickel catalyst in the presence of hydrogen and carbon dioxide at elevated temperatures. Since water ice is present on Mars, hydrogen could be produced though electrolysis of water. Combining these two reactions into a methane production system, Michel Lamontagne has provided a schematic of the whole process on marspedia.org. By design, the SpaceX Starship uses methane for fuel. The company may want to prioritize development of a flight-ready Sabatier reactor for this system to enable the transportation infrastructure needed for supplying a settlement until it can become self sufficient.
