Since the last update I've been working on getting asteroids fully into the game. I've got the asteroid details screen going and I decided to go with the standard S,C, and M types for now.
Asteroids will have anywhere from 1 to 4 squares that will basically be treated the same as planet squares. Each square can potentially have a mineral deposit or something of interest to investigate.
After I finish up asteroids, the only system objects left for me to complete will be comets, gas giant rings, and space stations.