De Carli, P. S., Xie, Z., & Sharp, T. G. (2010). All Shocked Meteorites were Shocked at Significant Depth in Their Parent Bodies. Meteoritics and Planetary Science Supplement, 73, 5427.
Shock waves have been important in the history of virtually all meteorites. Recent studies of melt veins in meteorites have indicated that many meteorites were deep within a parent body at the time of shock metamorphism. We have recently realized that it is virtually impossible for a meteorite to survive strong shock unless it is well below the surface of a parent body. The unconfined compressive strength of the strongest rocks is only about 500 MPa. To survive a stronger shock without being pulverized, the rock must be confined by surrounding material.