Human mission to Mars propellant from the Martian Atmosphere. This proposal drew on concepts developed by the former "Case for Mars" conference series. Over the next decade, Zubrin developed it into a mission concept, Mars Direct, which he presented in a book, "The Case for Mars" (1996). The mission is advocated by the Mars Society, which Zubrin founded in 1998, as practical and affordable. In 1991 in Toulouse, France, the International Space University studied an international human Mars mission. They proposed a crew of 8 traveling to Mars in a nuclear-powered vessel with artificial gravity provided by rotation. On the surface, 40 tonne habitats
Human mission to Mars intermediate steps before the landing on Mars, including human missions to Phobos; and the "Great Exploration" proposal from Lawrence Livermore National Laboratory, among others. In response to a presidential initiative, NASA made a study of a project for human lunar- and Mars exploration as a proposed follow-on to the International Space Station project. This resulted in a report, called the "90-day study", in which the agency proposed a long-term plan consisting of completing the Space Station as "a critical next step in all our space endeavors," returning to the Moon and establishing a permanent base, and then sending astronauts to