I honestly can't see that NASA (or anyone else for that matter) are doing shit to prevent impacts from anyone of the crap out there wiping out whole cities or causing something akin to a nuclear winter.
I also can't see how a manned Mars mission is liable to be preferable to sending machinery there, except for casting far more and achieving far less.
Overfishing is already causing problems, and these aren't going to get any better without measures being taken to remedy the problem.
If that's an example of my priorities being wrong, then I can live with that.
