The really scary part is just how close this comet came to hitting the Earth: since only Bonilla saw the fragments and no other astronomers did, that means that it had to be close to us. Very close. Very, seriously, it’s not even funny close. The minimum distance that the fragments passed was calculated to be about 400 miles from the Earth’s surface, which is nothing. That’s only 150 miles or so above the International Space Station. If the comet had been in a slightly different orbit, or had broken up at a slightly different time, as of about a hundred years ago, our entire civilization might have ceased to exist.

Anywhere from a billion to a trillion tons of comet passing as close as a few hundred miles from the surface of the Earth.