Given that the rocks of the solar system mostly travel on the disc, is there any considerable probability that impacts on the moon coming straight up and down can be interstellar rocks?
If axis-aligned meteorites are very rare, then perhaps there is a chance that a significant number of axis-aligned impacts come from interstellar objects.
It would be fun to search the polar regions of the moon for meteorite impacts that were axis aligned in the hope that the impactor would be interstellar. How unreasonable is it? If I put a square of foam on the moon for 20 years, and I checked afterwards which objects had hit the foam at high speed from an axis aligned vector, perhaps I could find a rock from elsewhere in the galaxy?