The only viable system of government is space is a socialist one. In the beginning that is. I know a lot of space enthusiast are of the capitalist persuasion, but capitalism isn't a good system for living one a space colony or station. I think this is one of the prime reasons that sci-fi tends to rely on military models since the military is the model of a socialist system.
When the lives of everyone relies on the lives of everyone else the capitalist system just won't work. You don't get to decide if you are going to be on latrine duty and you don't get to decide if you want to work in hydroponics today. You don't get to corner the market on air or water. You don't get to monopolize the new system of processing waste you invented so you can make money on it.
For the record, I am not making a mistake thinking that capitalism is a system of government. It is. Most people just like to think that it isn't.
Early on, the people doing the colonizing may be scientists, but they will be military scientists. Where some science fiction gets things wrong is in thinking that space will be like the wild west, with independent colonists lighting out for the territories and trying to make it on their own. The operation will in reality be military-industrial, and so the government such as it is will follow the needs of feeding the capitalist beast through its primary passageway, the military.
Those who will go there to settle will be representatives of one ot more governments. It is possible that more than one governments will create their own settlemwnts there and then the settlements there may loook like small replicas of earth.