In a NASA simulation of an asteroid impact, scientists concluded they couldn't stop a space rock from decimating Europe.

1. Earth orbits the sun in one year, hence the seasons of mild to stormy weather. Similarly, our solar system orbits the milky-way galaxy once about every 240 million years. Hence, the fluctuation of risk and exposure is probably seasonable within that 240 millions, but inevitable--not just to Kyper-belt asteroida, but to gravitational forces we can't even dream, or nightmare, about.

2. NASA may convert the simulation into a game and release it. I think there are gamers out there who would win and deflect the asteroids hitting Earth.