The probability of as asteroid coming anywhere near Earth in the range of possible danger is 1 is 500 million in 10 000 years. This information was a study done by NASA scientists in a report I read online not too long ago, so you can feel safe now :)
And as for the rest, I suppose it is a...
1w9.
You could say I was quite surprised at the results. I was expecting a 5 for main variant, but I guess 1w9 fits me pretty accurately albeit a few loopholes here and there.