Legend has it that Earth was a planet full of natural beauty and man-made wonders.  Then our greed and waste destroyed earth environment and brought destruction to humanity. Our ancestors were a group of elite who witnessed the horror of extreme weather, famine, war, and disease. In order to preserve their lives and the future of humanity, they fled to Mars and built this ecosystem.
However, as our population continues to grow, and the ecosystem can no longer support us. Meanwhile, without human civilization, the Earth has gradually recovered from the damages of mankind.  The elders in the ecosystem have decided to send us back to Earth in batches to explore and settle down. I just hope this time, we won`t repeat the same mistake.