The Belt

The Main Asteroid Belt, so called to distinguish it from the Kuiper Belt at the edge of the Solar System, is more commonly known as "The Belt".  It is a circumstellar disc that lays between the orbits of Mars and Jupiter.

The Belt contains nearly two million asteroids of over 1 km in diameter.  Over 200 asteroids are larger than 100 km; they are dwarved however by four of their number, that represent 50% of the entire mass of the Belt : Ceres (often classified, like Pluto, as a dwarf planet), Vesta, Pallas and Hygiea.

The material of the Belt is spread out sufficiently thin that spacecraft can travel through it with little danger.

The Belt provided key mineral resources to Earth (and, to a lesser extent, to Mars), and ice-farmers also provide water to the Outer Planets.  Nearly a billion people live on the main asteroids of the Belt, or spend most of their life working in it.  Belters, as they are called, make up a culturally distinct population, with their own language (formed from a mixture of various Earth languages), particular physical features caused by low or zero-G (greater height, larger heads, brittle bones reinforced by biomechanical implants).  This is reinforced by a strong sense of a common destiny, and continual mistreatment by the great powers that are Earth and Mars.

The Outer Planets Alliance (OPA) was a political organisation that actively supported independance for The Belt under a common government.  It was, in reality, a confederation of pro-independance political organisations, as the OPA have always have several leaders, rivals or not, whose exact agenda differ.  The OPA is classified was a terrorist organisation by Earth and Mars; notwithstanding, the OPA control de facto The Belt by 2340.

The "Eros Incident"was a major event in unifying the Belt; it was at the time unclear who was to blame for the deliberate infection of a million Belters by the alien proto-molecule; whether it was Earth of Mars, the very fact that they felt free to commit such atrocities showed the Belters that they needed to govern themselves.

Ironically, the fall of Earth in 2341, followed by the proto-molecule launch against Mars, came a little too soon.  No one leader had clearly asserted himself, and the newly independent Belt was slowly carved up by rival factions.  The main players are Fred Johnson on Tycho Station; Anderson Dawes, who is opposed on Ceres Station by Zig Ochoa;  Marco Inaros and his Free Navy; and the factions Black Sky and Golden Bough who have a high turnover in their leadership.  The situation is definitely not clear cut, no asteroid universally claiming allegiance to a particular faction, which is perhaps why Marco Inaros prefers to live out in space.