Space units need to be sent to space terrains to get mission rewards.Why can't I "train" or otherwise obtain Mission Rewards? I'm in Nanotech, I should be able to build just about all the solar system wonders etc. by now. I suppose it's because I'm not on a space map, but if so I'm sorry but that's ridiculous.. It's like saying there can be no Marco Polo's Journey if you don't have Kublai Khan and his capital Khanbaliq in your game.
Also you need space scenarios to build space buildings including wonders.
That is you need space map, if you want space exploration and colonization.
Transhuman era has very few earthly units - mega robots and nanobots

Galactic and later eras have few earthly buildings.
This was how Pepper created it back then before V38 release.
You should have picked my/tpehep/kation/snofru space maps since you wanted to play until end of tech tree.