Incidentally, about that “slight deflection” business:
One hears a lot about nuking an incoming asteroid as being a bad idea, as it then creates a lot of small pieces that cumulatively might do more damage than a single big hit. I think that might be debatable, esp. depending on the size of the pieces left, but there is a more important point. You don’t blast the thing while it is right on top of you, you blast it a couple weeks or more out. This puts almost all the pieces into trajectories that will miss the Earth / not get pulled into our gravity well. It does not take much (change in trajectory). Earth is really very small, and “2 weeks” in space / distance traveled is quite large.
Granted, this is harder to do than hitting the thing when it is a minute away, but it IS doable, even with present technology. The biggest problem is spotting the object in time.
Do we have an ICBM that can escape orbit? Could we ready a large enough rocket that could within a couple of weeks?