When you have rescued six miners, you will be able to leave the planet. To do so, you must fly through the accelerator rings to get enough speed to leave. When you see one, fly through it and then through the next ones after to gain enough speed to take off. While they appear in a straight line on the Blue moons, the rest of the time, they will appear in a zig-zag pattern, so be careful. If you miss one, watch for another series to try again.