 Astronomers did not observe large amounts of water following the collisions , and later impact studies found that fragmentation and destruction of the cometary fragments in an ' airburst ' probably occurred at much higher altitudes than previously expected , with even the largest fragments being destroyed when the pressure reached 250 kPa ( 36 psi ) , well above the expected depth of the water layer . The smaller fragments were probably destroyed before they even reached the cloud layer . 
