Landing a series of chemical processors to transform water and gases into usable products upon Mars is a first priority of settlement. These landers are delivered by a cargo carrier into orbit and then land independently. They are designed to take water from the ice-caps to electrolyse into hydrogen and oxygen, then use carbon dioxide from the atmosphere to combine with the hydrogen produced to form liquid methane. The latter then can be used to drive diesel engines, or power launch vehicles into orbit, combined with liquid oxygen. Follow the process at: http://www.eosmarsprogram.org/Page42-02-Gases.html