All this talk of Planet 9 perhaps being a primordial black hole (PBH) made me wonder how dangerous a PBH collision with earth would really be.
Specifically, if earth collided with a PBH of 1 earth mass, traveling fast enough that they didn't end up orbiting each other, what would happen?
Edit: From a paper asking Can one detect passage of small black hole through the Earth? the analysis was that for an approximately proton-volume and mountain-mass sized PBH
"It creates a long tube of heavily radiative damaged material, which should stay recognizable for geological time."
but is otherwise pretty hard to detect.
What would change if the PBH were the mass of the earth and the volume of a large marble? How slow would it have to be going before it really messed things up?