The challenge is simple, but a bit hard to define. Sorry about that but here goes.
Start a Science Mode game. No money. No contracts. You'll be busy enough trust me. Make it with (almost) any settings you want, but document them. Use any mods you want, but document them. Challenge yourself! The only setting you MUST have is that you MUST enable saves and reverts. Not many challenges require that one, eh? I would also suggest not making the science gathering all that difficult