Playing as the Thalan, I researched the extreme world colonization and all three extreme worlds, Aquatic, Barren and Frozen. I colonized Aquatic and Frozen worlds with no problem but I was unable to colonize a barren world.
Later in the game I had Atmospheric cleansing, Toxic World and Radioactive world. I was able to colonize those worlds but the barren world could not be colonized still. It was not the colony ship I was using as it worked for a toxic world afterwards.
