Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe

by Lisa Randall

Objects that form impact craters usually hit the ground at speeds up to eight times the Earth’s escape velocity, which is 11 km/sec, with roughly 20–25 km/sec most typical. For larger objects, this speed—many times the speed of sound—guarantees that an enormous amount of kinetic energy gets released, since kinetic energy grows not only with the mass but with the square of the speed. An impact on solid rock, which can be comparable to a nuclear blast, produces shock waves that compress both the object from space and the surface on Earth. The shock released on impact heats up the material it encounters and almost always melts and vaporizes the entering meteoroid, and—with sufficiently big meteoroids—regions of the target too.