Mars ISRU research for Mars is focused primarily on providing
rocket propellant for a return trip to Earth—either for a crewed or a sample return mission—or for use as fuel on Mars. Many of the proposed techniques use the well-characterised
atmosphere of Mars as feedstock. Since this can be simulated on Earth, these proposals are relatively simple to implement, though it is by no means certain that NASA or the ESA will favour this approach over a more conventional direct mission. A typical proposal for ISRU is the use of a
Sabatier reaction, , in order to produce methane on the Martian surface, to be used as a propellant. Oxygen is liberated from the water by
electrolysis, and the hydrogen recycled back into the Sabatier reaction. The usefulness of this reaction is that—, when the availability of water on Mars was less scientifically demonstrated—only the hydrogen (which is light) was thought to need to be brought from Earth. ,
SpaceX has stated their goal of
developing the technology for a
Mars propellant plant that could use a variation on what is described in the previous paragraph. Rather than transporting hydrogen from Earth to use in making the methane and oxygen, they have said they plan to mine the requisite water from subsurface
water ice, produce and then
store the post-Sabatier reactants, and then use it as propellant for return flights of their
Starship no earlier than 2023. As of 2023 SpaceX has not produced or published any designs, specifications for any ISRU technology. A similar reaction proposed for Mars is the reverse
water gas shift reaction, . This reaction takes place rapidly in the presence of an iron-chrome
catalyst at 400 °C, and has been implemented in an Earth-based
testbed by NASA. Again, hydrogen is recycled from the water by
electrolysis, and the reaction only needs a small amount of hydrogen from Earth. The net result of this reaction is the production of oxygen, to be used as the oxidizer component of rocket fuel. Another reaction proposed for the production of oxygen and fuel is the electrolysis of the atmospheric carbon dioxide, : \overset{atmospheric \atop {carbon\ dioxide}}{2CO2} ->[\text{energy}] {2CO} + O2 It has also been proposed the
in situ production of oxygen, hydrogen and CO from the Martian
hematite deposits via a two-step thermochemical /H2O splitting process, and specifically in the
magnetite/
wüstite redox cycle. Although
thermolysis is the most direct, one-step process for splitting molecules, it is neither practical nor efficient in the case of either H2O or CO2. This is because the process requires a very high temperature (> 2,500 °C) to achieve a useful dissociation fraction. This poses problems in finding suitable reactor materials, losses due to vigorous product recombination, and excessive aperture radiation losses when concentrated solar heat is used. The magnetite/wustite redox cycle was first proposed for solar application on earth by Nakamura, and was one of the first used for solar-driven two-step
water splitting. In this cycle, water reacts with wustite (FeO) to form magnetite (Fe3O4) and hydrogen. The summarised reactions in this two-step splitting process are as follows: : Fe3O4 ->[\text{energy}] {3FeO} + \overbrace{1/2O2}^{\underset{(\operatorname{by-product})}{oxygen}} and the obtained FeO is used for the thermal splitting of water or CO2 : : : This process is repeated cyclically. The above process results in a substantial reduction in the thermal input of energy if compared with the most direct, one-step process for splitting molecules. However, the process needs
wüstite (FeO) to start the cycle, but on Mars there is no wustite or at least not in significant amounts. Nevertheless, wustite can be easily obtained by reduction of hematite (Fe2O3) which is an abundant material on Mars, being especially conspicuous are the strong hematite deposits located at
Terra Meridiani. The use of wustite from the hematite, abundantly available on Mars, is an industrial process well known on Earth, and is performed by the following two main reduction reactions: : : The proposed
2001 Mars Surveyor lander was to demonstrate manufacture of oxygen from the
atmosphere of Mars, and test solar cell technologies and methods of mitigating the effect of
Martian dust on the power systems, but the project was cancelled. The
Mars 2020 rover mission included an ISRU technology demonstrator (the
Mars Oxygen ISRU Experiment) that extracted CO2 from the atmosphere and successfully produced 5.37 grams of O2 over an hour. It has been suggested that buildings on Mars could be made from
basalt as it has good insulating properties. An underground structure of this type would be able to protect life forms against radiation exposure. All of the resources required to make plastics exist on Mars. Many of these complex reactions are able to be completed from the gases harvested from the martian atmosphere. Traces of free oxygen, carbon monoxide, water and methane are all known to exist. Hydrogen and oxygen can be made by the electrolysis of water, carbon monoxide and oxygen by the electrolysis of carbon dioxide and methane by the Sabatier reaction of carbon dioxide and hydrogen. These basic reactions provide the building blocks for more complex reaction series which are able to make plastics.
Ethylene is used to make plastics such as
polyethylene and
polypropylene and can be made from carbon monoxide and hydrogen: : .
Moon The Moon possesses abundant raw materials that are potentially relevant to a hierarchy of future applications, beginning with the use of lunar materials to facilitate human activities on the
Moon itself and progressing to the use of lunar resources to underpin a future industrial capability within the Earth-Moon system. Natural resources include solar power, oxygen, water, hydrogen, and metals. The lunar highland material
anorthite can be used as
aluminium ore. Smelters can produce pure aluminium, calcium metal, oxygen and silica glass from anorthite. Raw anorthite is also good for making fiberglass and other glass and ceramic products. One particular processing technique is to use
fluorine brought from Earth as
potassium fluoride to separate the raw materials from the lunar rocks. Over twenty different methods have been proposed for
oxygen extraction from the lunar regolith. Oxygen is often found in iron-rich lunar minerals and glasses as
iron oxide. The oxygen can be extracted by heating the material to temperatures above 900 °C and exposing it to hydrogen gas. The basic equation is: FeO + H2 → Fe + H2O. This process has recently been made much more practical by the discovery of significant amounts of
hydrogen-containing
regolith near the
Moon's poles by the
Clementine spacecraft. through processing techniques such as
sintering, hot-pressing,
liquification, and the cast
basalt method. Cast basalt is used on Earth for construction of, for example, pipes where a high resistance to abrasion is required.
Glass and
glass fiber are straightforward to process on the Moon and Mars. In August 2005, NASA contracted for the production of 16 tonnes of simulated lunar soil, or
lunar regolith simulant material for research on how lunar soil could be used
in situ.
Martian moons, Ceres, asteroids Other proposals are based on
Phobos and
Deimos. These moons are in reasonably high orbits above Mars, have very low escape velocities, and unlike Mars have return
delta-v's from their surfaces to
LEO which are less than the return from the Moon.
Ceres is further out than Mars, with a higher delta-v, but launch windows and travel times are better, and the surface gravity is just 0.028 g, with a very low escape velocity of 510 m/s. Researchers have speculated that the interior configuration of Ceres includes a water-ice-rich mantle over a rocky core.
Near Earth Asteroids and bodies in the
asteroid belt could also be sources of raw materials for ISRU.
Planetary atmospheres Proposals have been made for "mining" for
rocket propulsion, using what is called a
Propulsive Fluid Accumulator.
Atmospheric gases like oxygen and
argon could be extracted from the atmosphere of planets like the Earth, Mars, and the outer
giant planets by
Propulsive Fluid Accumulator satellites in low orbit. ==ISRU capability classification (NASA)==