I just brought up the subject in a recent thread. So the estimated stats on this impactor were:

Comet "only" 50-100 kilometers in diameter. Too bad there aren't any photos this time.
Impact velocity somewhere between 50-100 km per second. Again, too bad there's no astrometric data. There was no warning for this impactor. At least for Shoemaker-Levy 9 we had just over a year of observations.

Shoemaker-Levy 9 impacted Jupiter just 15 years ago and cut loose about 6 million Megatonnes from each of 20 fragments. Of course this is just one big chunk, approached from the dark side, and no one saw it coming. Typical non-periodic comet.

Alot of people think this is a rare event. However we know it is only a matter of time until a comet or meteor comes our way.

Like I said before, if we were at war and the enemy was building a doomsday device, it would also be just a matter of time. Would we sit back, and say that the risk is minimal? Would risk even be discussed? It only takes one doomsday device and we're done.

Any risk at all is unacceptable.

A threat countermeasure would push back the envelope of safety, create a map of deep space to a distance of 50-100 AU, to give us ample warning to launch a starship to intercept potential impactors. The starship might be able to nudge the impactor off course and away from Earth.

Starships need nuclear propulsion. The Comprehensive Test Ban Treaty prohibits the development of any such vehicle that operates in Outer Space.

I propose to amend the CTBT and define Deep Space as distinct from Outer Space. Outer Space would be defined as the space outside Earth's atmosphere but not extending beyond the habitable zone of our solar system. Deep Space would be defined as any volume of space outside the habitable zone. I believe it would be acceptable to test nuclear propulsion systems outside the habitable zone.

This matter is in the purview of The Diplomats.