I know this is going to be mildly pedantic, but if it were an asteroid/meteorite, we would've known it's trajectory and impact point for years in advance. Especially if it's big enough to cause a calamity.
Honestly, my mind is sort of thinking of all the possibilities. When, then, would it be the best time to let the public know of this event?
A more plausible* 'instakill' event would be a record Coronal Mass Ejection directed at Earth when our magnetic field is so weak it has no chance of repelling it.
*possible/less likely to provide any significant survivors in the long term, and far less loose ends.
Less pedantic answer? I'd like to know about the location of the arks.
