[fastball]

Of course it's unlikely. Being visited by an alien race is, in fact, highly unlikely.

That's not the point, though, is it? This article said "experts say that creating materials we don't understand is impossible." Not unlikely - impossible.

An alien race with the capability to visit earth would have a grasp of physics that we obviously do not, otherwise we would be visiting habitable planets right now. That's the whole point. The argument this article puts forth is just as silly as the young-earth creationist argument that "abiogenesis is incredibly unlikely, so it must be God". Or in this case "we don't understand it, so it must be impossible".