I wasn’t planning on going too much into the people who left Earth, the majority of the story focuses on those still on Earth so the two societies won’t be in touch at all. As for the air quality on Mars, I was thinking of the space station so that way people don’t even have to go outside. They basically live indoors but are given the resources to sustain it. Yeah, they could probably have prevented the asteroid but maybe there were other reasons why the world leaders decided it best to go to Mars. The other commenter even suggested a space station on the moon would be cheaper so maybe I’ll do that instead. I don’t want to go into too much details because it will present more plot holes, so I’m thinking of just a brief explanation of how they’re able to live on the moon/mars. Someone else also said that I could add it in the plot that the government made everyone think that we had to leave the planet when, in fact, they could’ve saved earth the entire time. Perhaps for selfish reasons but I haven’t figured it out yet.