Mining the Martian Regolith for Water

It has been thought for some time now that the human exploration of Mars will depend ultimately on our ability to utilize Martian resources. Zubrin's Mars Direct and NASA's Reference Mission for the Human Exploration of Mars both assumed that propellant and life support consumables could be obtained from the atmosphere of Mars. Various approaches to utilizing the Martian atmosphere as a source of oxygen have been studied, along with the reduction of CO2 to methane, but in all cases it has been assumed that hydrogen must be brought from Earth. This is not an overwhelming problem, as the hydrogen is only a small part of the total propellant requirement (1/12 in the case of CH4-O2; 1/9 in the case of H2-O2). However, even this is a burden because hydrogen tanks generally are about as massive as the hydrogen they contain and either power or multi-layered insulation or both have to be provided to keep hydrogen liquefied from Earth to Mars. This reduces the effectiveness of propellant production on Mars, but it is still enabling for some missions for the Mars to orbit leg of the return home. A readily available source of water can be very beneficial to the performance of missions to Mars, by removing this dependency on imported hydrogen.