In case of collision, approximately one chance in 120 000, the shock would be very violent. 35 millions megatons of TNT, more than 2 billions times the power of the Hiroshima bomb.
http://www.youtube.com/watch?feature=player_embedded&v=1T2eBSexgX4
http://www.youtube.com/watch?feature=player_embedded&v=1T2eBSexgX4