[Perspective] Revealing the dynamics of a large impact
Steady as a rock. We all know what to expect of rock. Rocks deform infinitesimally slowly. Earth scientists get excited at the prospect of “rapid” plate movements that average the same speed at which our fingernails grow. Humans don't make much impact on rocks, except at the most puny of scales. Sometimes nature does experiments for us that we could never do for ourselves: When a large meteorite hits the planet, interactions occur that are far outside our normal experience. The outer surface is deformed with a force and strain rate that we cannot begin to reproduce; rocks flow like fluid, very fast and on a huge scale. On page 878 of this issue, Morgan et al. (1) present results from a drilling expedition into the Chicxulub crater that reveal how the formation of peak rings in large impact craters occurs. Numerical simulations of the impact model the time scale...