A feasibility study is carried out for Mission MILESTONE, which is a short duration mission with the aim of establishing a long permanence outpost for subsequent exploration. This paper presents the results of this study, both the overall system architecture and the results of detailed investigations into certain aspects of the mission. The Mission MILESTONE (Mars Initial Landing ExpeditionsTowards a New Era) feasibility study focuses on the mission stages from Low Mars Orbit onwards only, and does not carry out a detailed investigation into the Earth-Mars transit. An 180 day transit is assumed each way, with the intention of residing on the surface for 60 days. As the mission is intended as a pre-cursor to exploration missions, it is focused on the establishment of a habitable environment to ensure the supply of sufficient resources required to sustain human life. During this first manned mission to the Martian surface there will also be technology demonstrations, increasing technology readiness levels for the benefit of future missions. This paper first of all sets out the mission architecture and objectives. It then details the results of the major investigations carried out into key components of the mission and outpost. Finally, the main conclusions of the feasibility study are drawn.