Is there any action that could have been taken? Genuinely curious, I read about a test of some technology for deflecting asteroids a few weeks ago on HN, but I don't think we really have those capabilities yet?
There is likely a capability in the classified world to launch a vehicle to hit this object, but it won't be used because disclosing this ability would spark an arms race.
“Hit” and “do something useful” would seem to be distinctly different questions. A rock that you discover just before it hits us can’t be easily deflected, and even if you destroy it all of the mass is still headed our way.
I don't know what action could be taken. The risk of mass anxiety and the behavior that comes with that is probably greater than any additional safety a vague 3 day warning would provide.
I would want to know, especially if it’s a large object and higher percentage probability, because then it’s a way to tell loved ones what we need to tell them and go forward together in love. We should always strive to do this, of course, but it would still be better to have the opportunity to do it.