[russdill]

There will be plenty of other interstellar objects that pass through our solar system. Oumuamua wasn't some special once in a lifetime event, it's just we are just getting the capability online to see these objects. We will see these objects earlier and earlier, we will see a lot more of them, and in all likelyhood future missions will intercept such objects. Maybe even sample return someday.

[euroderf]

So what is the chance that one will be made of antimatter ? Somewhere close to nil ?

[russdill]

It would not make it very far as it passes though interstellar gas that is not antimatter.