Here is the full list of all 25 Interplanetary achievements.
Win 10 single player games.
Destroy 100 cities over any number of games.
Grow five cities to their maximum populations.
Beat the Impossible AI.
Defeat two enemy planets in one turn.
Unlock all technologies.
Hit your own planet with a railgun.
Have 25,000 material in stock.
Build 200 buildings on your planet.
Defeat an enemy planet.
Fire all the superweapons during the same turn.
Fire Asteroid Diversion superweapon.
Have your planet run out of material.
Produce 7,000 Energy in one turn.
Fire Solar Laser superweapon.
Win an online multiplayer match.
Win 5 online multiplayer matches.
Win 10 online multiplayer matches.
Win 50 online multiplayer matches.
Win 100 online multiplayer matches.
Win 100 single player games.
Win an online multiplayer match with at least two players.
Win an online multiplayer match with at least four players.
Win an online multiplayer match with eight players.
Win a match with barely any population left.