The exploration and colonization of Mars, as discussed in the more than 130 papers and essays from the Mars Society's annual conferences, is presented in this second volume of the On to Mars series. Formed in 1998 to support the exploration and settlement of Mars, the Mars Society seeks to educate and convince political powers, industry leaders, and the public about the necessity of committing resources to the development of a Mars settlement program. Covering recent technological and planning advances, these essays cover the last three years of Mars Society meetings and discuss such topics as habitat infrastructure, exploration technique, and colony organization as they have been explored at the Mars Society's Analog Research Stations at Devon Island, Nunavuit in Canada and in Hanksville, Utah. Two short videos, "Stepping Stones to Mars" and Robert Zubrin's testimony before the Senate Committee on Commerce at the Hearings on the Future of the U.S. Space Program, are featured on the included CD-ROM.