Steve - I have run into what has to be a bug in planet/system generation. Or I have run into something I've never encountered before.
One of my fleets was probing a system, as I've grown cautious after losing several survey ships in systems with planets with oxygen-nitrogen atmospheres. The fleet was proceeding towards a habitable moon of a gas giant when it detected a population on the gas giant. I double checked and the population was actually on the gas giant, not any of the moons, and it appeared to be composed of ground troops. Thinking that maybe I had found something new that you've added, I sent in my geo-survey ship to survey the gas giant and began trying to establish contact with the aliens. When the survey ship competed its survey it revealed that the gas giant had deposits of all eleven TN resources at good availability levels. This should not be possible, unless things have changed a lot.
At this point I thought that maybe Aurora was calling the planet a gas giant but that it really was a terrestrial planet in all but name, but that doesn't seem to be the case. Aurora would not allow me to establish a colony on the gas giant, and informed me that it wasn't possible on a gas giant, just as it should have. The gas giant has 10 moons, three of which are terrestrial, just as a gas giant might have but a terrestrial planet will not have.
The fact that Aurora allowed the NPR to establish a colony on the planet is interesting, given it would not allow me to do the same thing. I think for now I am going to ignore the alien colony as if it doesn't exist, as it shouldn't exist.
Kurt
Steve- I forgot to add that I'm using version 6.3.