i thought the marauders were supposed to start from the sun in some way...
well, last game i saw some marauders emerging from thin air:


so, bug or feature?
i have a save game that always generates those marauders at one of my planets (though a different one on every reload), entering from somewhere above the planet plane, and a save at the point of the screen shot if necessary, just tell me where to send them if you need those...