You bring up a great point that should justify in everyone's mind the existence of NASA: the seeking out of planet killing asteroids (or at least asteroids big enough to be extinction causing).

Unfortunately no one can see that far ahead of their day to day problems so if the next one is heading towards us we're fucked. And did you know that during extincition events life that is over 100 pounds tend to be the life forms that are wiped out. Smaller life forms tend to be able to survive the event with a greater level of success.

You call them life threatening but I wonder if any acctually have life locked away in their frozen matrix.

We may be able to spot/count/label, but we still can't do a damn thing about them.

If only 911 of those big "asterorids" have been found, how do they know there are 981 of them?

Reposting someone else's half-baked blather does not add value.

Good news, now that we know what they are and where they are, we just need to focus on exploration outside out own moon, so we can send ships to those rocks and mine the crap out of them.