Because we are a migrant species... and because of this: http://www.greatdreams.com/asteroid-map.jpg http://www.greatdreams.com/asteroid-map.jpg All those nice

Because we are a migrant species... and because of this: http://www.greatdreams.com/asteroid-map.jpg http://www.greatdreams.com/asteroid-map.jpg All those nice dots are potentially dangerous asteroids :) And also, to prove we can.