Earth Theory - Gamma Ray Burst (GR
What about it?
My theory of what happened to Earth is that is was hit with a Gamma Ray Burst (GR. They would never see it coming because it travels at light speed and a relatively close one would instantly sterilize one side of the Earth and destroy the entire atmosphere.
I'm thinking the timeline will be Earth established a few small colonies, GRB hits and destroys Earth, colonies come together and cooperate due to lack of resources from Earth's destruction, colonies eventually splinter and go to war over resources, game takes place after the colony wars.