To counter your point on an intellectual level, yes...Jupiter and Saturn are gas giants with scientifically impossible surfaces to traverse. But...the surface of Venus and Mercury are also impossible to traverse scientifically, but through the Traveler humanity colonized both. What makes doing so on Jupiter and Saturn so impossible? This IS the same universe that the Vex pretty much terraformed the entire planet of Mercury into a machine. Is it so unbelievable that golden age humanity couldn't have done the same to the actual surfaces of the gas giants?