Space Colonies

In the XXII Century humans manage to colonized new planets across the stars with the pure objective to gather resources for cleaning and decontaminate Planet Earth.   A few years before the colonization, enormous space stations were built between each selected planet working as checkpoints or tollbooths between colonies. The few animals that survived the high temperatures of the environmental crisis were moved into the stations closer to Planet Earth.   In total there were built 8 stations in a chain-like manner with 1 station each between two planets, the closer a colony was to Planet Earth the most advanced it was, due to the time being operational.