A lot of people worldbuild when they daydream and have the bones of a story kicking around in their brain, but have to pay the bills and raise the kids etc so they never flesh it out and write it down. What’s your story’s premise? Fantasy, sci-fi, alternate history, mystery, western, whatever genre.
Mankind has started colonizing the solar system, including installing a satellite at the Sun-Mars L1 Lagrange Point to protect Mars from solar radiation and dumping a ton of water and methane ice on Mars until it is able sustain a thicker atmosphere and liquid water on the surface. Then, Kessler syndrome hits Earth Orbit, which causes a chain of events that collapses society on Earth.
Thousands of years later, it is found that there are now landing paths to get back to Earth, even though these paths are sporadic. A Lunar nation invites a Martian nation to team up to explore Earth and what is left of humanity.