Successfully planning a manned mission to Mars involves an extraordinary balance of resources, risk, technology development and innovation. The inter-dependency of these factors will ultimately drive out the more feasible scenarios for supporting humans during three year, or longer, missions to the Mars surface and home to Earth. Based on a mission profile developed in the Exploration Programs Office at the Johnson Space Center, the Flight Crew Support Division began developing conceptual Mars surface habitats to drive out the early human support issues and habitat development concerns. Following the completion of an analysis of a horizontally oriented and outfitted Initial Lunar Habitat (ILH), the decision was made to focus on a vertically oriented habitat as a comparative study. Drawing from the results of both KC-135 partial gravity locomotion testing and water immersion vertical translation studies, the Initial Mars Habitat (IMH), is an analysis of the habitat systems, volume, and capabilities required to support the first crew of six on the surface of Mars for 500 to 600 days.