Tapestry
How do space tiles get onto the Aliens civilization mat, and when do you discard one?
At each income turn from the second on, discard the tile on the Aliens mat only if there is one, then choose either to explore a new space tile or to gain one resource. You start with 4 space tiles in your supply, so on your 2nd income there is no tile to discard and you can place one from your supply; by your 3rd income you will usually have one on the mat to discard first.