The Mars Colonies are a group of 19 subterranean super cities built below the surface of Mars by the Brayburn Society to house all of their people and give them a home away from Earth where they could practice science in peace. Each colony is entirely self supporting, with their own underground food production, livestock, water and sewage treatment, and much more. Each colony is completely independent and capable of operating on their own, completely isolated from all outside intervention, including ores and mineral resources and much more. Each one is also able to comfortably house and support up to one million people each, although most colonies only operate at about 80% capacity at any given time. But, even though they don't need outside assistance, inter-colony trade and commerce is alive and well, and very brisk at times, and they do receive outside shipments of resources, while in turn producing usable products that are shipped and sold elsewhere. They are also the primary supplier of everything that Earthfleet, or its various support organizations, like the Saturn Shipyards or Pluto Station, needs in order to maintain daily operations.