Colonisation of mars has been tried but failed dismally.
In an effort to escape the growing pressure, groups of people have borrowed technology from the Mars project, adapted it to underwater conditions and built colonies on the seabed. Over several years they have linked these underwater cities to become an extended nation now known as Maress.
The Teresians, (those left on the land surface), are jealous of the high quality of life that the Maresians have developed by utilizing the resources of the seabed and have discovered that they are on the verge of perfecting the use of Zero Point Energy. Knowing that this technology will provide limitless energy the Teresians have turned to military action to wrest the technology from the undersea dwellers.
A third, neutral, group of nomadic traders exist on the sea surface and in Earth orbit. Both the Maresians and the Teresians deal with them. Various alliances are constantly being formed and dissolved with the 'Nutes' by both sides. Their surface base is a group of artifical floating islands. The main one of these is connected by the 'Space Loop' to an orbiting base built using a hollowed out Asteroid. As the Nutes have very few resources or food production capability, they make a living by transporting Maresian and Teresian garbage into space to be shot into the Sun. With land space at a premium, cryogenic storage or burial of the dead is prohibited on Earth so the Nutes provide space based storage for frozen bodies. In return for providing the Space Loop facility, they gain goods and money. They also maintain an active information and junk trade. The Maresians and the Teresians use this to gain intelligence on each other. The Nutes are fond of gambling and live a rough life centered around the Space Loop Facility, trading, casinos and Flywheeler and Freewheeler racing.