The Technology Transfer and Partnerships Office
Oxygen from Regolith

Our current knowledge of rocks and regolith throughout the solar system reveals that the vast majority of solid surface planetary objects are composed of silicate minerals as their primary constituents. The early history of the formation of each object and its geological evolution result in significant differences in the mineral signatures and abundances in planets, moons, asteroids and comets. They all share a mineralogy based on oxides of metals and as a result all possess large amounts of oxygen bound in their rocky materials.

The samples of lunar rocks and regolith brought back to Earth by the astronauts of the Apollo missions and the meteorites found on Earth have provided this kind of direct knowledge of oxide compositions. Remote sensing of the surfaces of other planetary objects and the in-situ work performed by the Mars rovers have completed this picture. The table below shows the oxide compositions found in several lunar samples.



Chemical composition of several lunar samples identified by their Apollo mission number (A11=Apollo 11). The major oxides represented comprise 98 of the lunar crust. (Source: J. Plescia/J. Hopkins U.)

Chemical composition of several lunar samples identified by their Apollo mission number (A11=Apollo 11). The major oxides represented comprise ~98% of the lunar crust. (Source: J. Plescia/J. Hopkins U.)



in lunar samples

The ubiquity and abundance of oxygen in rocks and soils in space (42–45% by weight in lunar samples) incite scientists and engineers to devise the most efficient techniques to extract it. The uses of oxygen by spacecraft and human crews far from Earth are many ranging from life support as gas and a component of water to propulsion oxidizer and plant growth. The extraction of oxygen from minerals however is achieved at a high energetic cost because metal oxides are very stable compounds and the separation of these compounds requires direct energy and/or chemical reagents. These costs remain in favor of ISRU when one compares the cost of launching any amount of supplies from Earth and that cost increases with distance in space. Many experts see the extraction of such an essential commodity as oxygen on other planets as a critical step without which human missions in deep space will involve too much risk.


The ISRU Technology Development Project has focused its research and development efforts on three main technological routes in recent years: the carbothermic reduction of regolith, the hydrogen reduction of regolith and molten regolith electrolysis.