Here is the full list of all 15 The Space Garden achievements.
Collect 100.000 coins
Defeat 100 aliens
Get 100 helpers
Get your first guardian
Survive to your first zombie attack
Collect 10.000 coins
Collect 1000 coins
Get your first chicken
Defeat an UFO
Get your first helper
Collect 100 coins
Get your first plant
Place your first face on a planet
Connect all your planets
Survive to your first alien invasion