Table III: Lunar Materials Available The depth of the lunar soil, or regolith, varies considerably with location. The regolith depth of mare surfaces ranges from 2 to 10 meters (references #5 and #6). The highland areas, which are by far the oldest lunar features, have developed regoliths hundreds of meters to possibly kilometers deep (references #7 and #8). Mining, beneficiation, and processing of lunar materials to produce propellants and useful construction materials has received significant study and some experimental work. Recent SSI-funded laboratory experiments by Rockwell International Corporation have demonstrated that chemical processing techniques can successfully separate needed elements with very little loss of reagents. For the purposes of this lunar material constructed SPS study, it should be assumed that if a needed element exists in lunar material, it can be successfully recovered and used for SPS fabrication.