Space element is needed in Little Alchemy for the associated elements such as Astronaut, Telescope, Planet, Rocket, Meteoroid, Alien, and Space Station. You have three ways to make Space, all of them need to make Sky and Star first, some of them need Moon and Sun elements. Check out the detailed instructions and try it yourself.
Fire + Water = Steam
Steam + Air = Cloud
Cloud + Air = Sky
Earth + Fire = Lava
Lava + Air = Stone
Sky + Stone = Moon
Sky + Moon = Night
Sky + Night = Star
Method 1: Sky + Star
Sky + Star = Space
Method 2: Star + Sun
Sky + Fire = Sun
Star + Sun = Space
Method 3: Star + Moon
Star + Moon = Space