My first foray into the world of Illustrator involved using this tutorial:
http://blog.spoongraphics.co.uk/tutorials/how-to-create-a-dark-lunar-poster-design-with-ps-ai
Although still most of it was done in PS, I do want to learn Ai eventually. Anyway, I've attached what I came up with.
Any critique would be appreciated, obviously it was done via the tutorial so it wasn't my idea originally, but I've tried to add a variation on the original 'Lunar' poster.
I personally prefer the Mars one, the Europa one is maybe a bit too busy.