As far as I remember from physics Milcho is right - atmosphere at that speed is like hitting brick wall.
According to report from NASA the object had diameter of maximally 17 m, mass around 10000 tonnes (a really heavy one, because their density is often less than water density) and velocity 17900 m/s. Kinetic energy of this object is 1602050000000000 J = 1602 TJ. Energy equivalent (in TNT) of this kinetic energy value is around 383 kTons of TNT - e.g. we need at least 383 kTons of TNT equivalent energy to just stop the motion of the meteorite. Assuming that energy of explosion must be higher than just kinetic energy (it's calculated using the thermodynamic energy of detonation) - we could get somewhere to 500 kTons.