No matter how infinitesimally small the probability - the universe is infinite, and so it probably will happen.

i3 is much bigger than the Chicxulub asteroid that ended the Cretaceous period (and extinct all non-avian dinosaurs).

An object (depending on consistency) of about 100m is enough to wipe out a city and do enough damage to the environment. Something of 8-20km is in the same category as what wiped out the dinosaurs (10-15km).

No, I can’t really imagine what that means, either.