How does a planet become depleted and how do I recover it?

I recently conquered an enemy's star system. I noticed that a few planets were "depleted". How does a planet become depleted?

Since only planets from conquered systems seem to be depleted, does it have something to do with the invasion? Or with the enemy, whose planets I conquered, being Cravers?

And, is there any way to recover depleted planets?

1 Answer

Depletion is caused by the Craver affinity, and occurs after the planet has been under craver control for 60 turns. The effects cannot be undone.