orbit. Lunar water ice Lunar scientists had discussed the possibility of water repositories for decades. They are now increasingly "confident that the decades-long debate is over" a report says. "The Moon, in fact, has water in all sorts of places; not just locked up in minerals, but scattered throughout the broken-up surface, and, potentially, in blocks or sheets of ice at depth." The results from the Chandrayaan mission are also "offering a wide array of watery signals." It is estimated there is at least 600 million tons of ice at the north pole in sheets of relatively pure ice at least a couple of meters thick. Solar power satellites Gerard K. O'Neill, noting the problem of high launch costs in the early 1970s, came up with the idea of building Solar Power Satellites in orbit with materials from the Moon. Launch costs from the Moon would vary significantly if the Moon is industrially developed (see "Launch costs" above). This proposal was based on the contemporary estimates of future launch costs of the Space Shuttle. On 30 April 1979, the Final Report "Lunar Resources Utilization for Space Construction" by General Dynamics Convair Division under NASA contract, NAS9-15560 concluded that the use of lunar resources would be cheaper than terrestrial materials for a system comprising as few as thirty Solar Power Satellites of 10 GW capacity each. In 1980, when NASA's launch cost estimates for the Space Shuttle were grossly optimistic, O'Neill et al. published another route to manufacturing using lunar materials with much lower startup costs. This 1980s SPS concept relied less on human presence in space and more on partially self-replicating systems on the lunar surface under telepresence control of workers stationed on Earth. See also Aurora programme Colonization of Mars Federation of Galaxy Explorers Human outpost In situ resource utilization Lunar Explorers Society Lunarcrete Lunarcy! Moon in fiction Moon landing Moon Society National Space Society NewSpace Planetary defense Planetary habitability Space architecture Space Frontier Foundation NASA lunar outpost concepts References Notes General references Further reading Resource Utilization Concepts for MoonMars; ByIris Fleischer, Olivia Haider, Morten W. Hansen, Robert Peckyno, Daniel Rosenberg and Robert E. Guinness; 30 September 2003; IAC Bremen, 2003 (29 Sept – 03 Oct 2003) and MoonMars Workshop (26–28 Sept 2003, Bremen). Accessed on 18 January 2010 Publisher's book page. External links NASA Ames Research Center Eureka! Ice found at Lunar Poles. Retrieved December 18, 2004. Cornell