Apparently we’ve just realized that it’s due to global warming:
“...Whats coming our way? Is this an effect of, perhaps, of global warming, or is this just some meteoric occasion? CNNs Deborah Feyerick asked Bill The Science Guy Nye, head of the Planetary Society, in a Saturday segment...”
http://www.foxnews.com/science/2013/02/11/cnn-anchor-blames-asteroid-on-global-warming/
I guess global warming makes earth a magnet for the ‘roids?