Well, NEO site saying this: http://www.jpl.nasa....elease=2013-061 interesting to note the size and that they say it was ment to graze the atmosphere (so possible that gravity forced it to strike). Still though, Russia will have a better idea of what the circumstances are regarding this at the moment. I say "ment" like they knew about it, but they actually said looks like it was going to graze, or something to that effect.