[magicalist]

> If a black hole with a mass of, say, Ceres hit the Earth, it would not be particularly worse than if Ceres hit the Earth.

This equivalency is true for many aspects of orbital mechanics (depending on setup giving sufficient distance), but I don't believe that's true at all for a collision. Someone with more knowledge correct me, but a black hole with the mass of Ceres would be very tiny but also emitting a ton of radiation. The collision would be very different.

[margalabargala]

I more mean that the resulting moon-sized fragments of what used to be the earth would be equally devoid of life. I agree the physics might vary somewhat.

If the black hole had a mass more similar to a 0.5-mile asteroid...well, I'm not sure what would happen. Would it just punch a hole straight through the earth?