What about andvanced tech on an empty planet?

[Paladin]

I found two empty, rock planets in different systems, whose sensor description said advanced technology had been detected on them. Since there was no colony on them, I tried to bring scouts there, even put a colony on top of it, but I could not find how to investigate those further.
It was not one of the fancy decorative descriptions we find on other plantes, it had a blue dot listing there was something special about them, and also a kind of "Stonehenge" icon besides the planet's name, kinda ruin-type icon...
As I understand, some planets are supposed to have special bonuses on it, like the small huts in CIV2... That might be it, if I could just find a can openner...

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Redemption is our goal...
B ))