Eighty million trees stripped bare and blown down in a radial pattern around a blast point, similar to a nuclear explosion except that this was 1908. As we know now, Siberia was hit by an asteroid. In fact, 100 hundred years ago this monday. As we've explored our own solar system in the last 50 years we see that Tunguska-sized events, at least on other bodies, are not uncommon. And planet shaping events, like what happened to Mars, are uncommon in our time scale, but never impossible. Recently, H.R.6063 made provision for tracking of near-Earth objects: "recommend a Federal agency or agencies to be responsible for protecting the Nation from a near-Earth object that is anticipated to collide with Earth and implementing a deflection campaign" and "a low-cost space mission with the purpose of rendezvousing with and characterizing the Apophis asteroid, which scientists estimate will in 2029 pass at a distance from Earth that is closer than geostationary satellites".