[fastball]

We already know for a fact that there are units of matter smaller than protons/neutrons/electrons. As such, x-ray diffraction is obviously not sufficient to analyze all matter.

[mindcrime]

We already know for a fact that there are units of matter smaller than protons/neutrons/electrons.

Yes, and everything we know about them suggests that they either:

Decay almost immediately when encountered in the wild

Immediately clump together with other particles to form larger units

Do not interact with normal matter

Etc.

IOW, there's little or no reason to think that any kind of stable material, anything that you could store in a warehouse as a clump of "stuff", is made without atoms.

If it is possible, as far as I know, that would be deep into "entirely new physics that violates a lot of central tenets of our current thinking". So yeah, that could happen, but you have to ask "is it likely"?

[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".