Still, it would be very fascinating to ponder, if an alien spaceship wreck just drifted through our solar system... how could we tell it is one?
We can't without taking a closer look, really. So to be sure that it isn't an alien spacecraft, we would have needed to throw some money at it. Since nobody was willing to do that, Okhams razor is really all that's left.
And it heavily favors the not-alien-spaceship assumption, unless for some reason you assume that alien spaceship wrecks are ridiculously common in the galaxy :lol: