An on-orbit demonstration of asteroid deflection is a key test of our ability to defend the planet from an incoming asteroid. The recent DART (Double Asteroid Redirection Test) mission was NASA’s demonstration of kinetic impactor technology, impacting an asteroid to adjust its speed and path. The DART spacecraft impacted the asteroid Dimorphos on September 26, 2022, and was the first-ever space mission to demonstrate asteroid deflection by a kinetic impactor. We discuss the mission, and the critical role that mechanics plays in such planetary defense missions.

Most asteroids are “small” rocky bodies (they can vary in size from sub-m to several hundred km). The structure and surface topography of asteroids are determined by impact and fracture processes that occur over an immense range of timescales. Recent observations have demonstrated that many small asteroids are “rubble-piles,” collections of rocks held together by gravity. What determines this structure? We examine the disruption and breakdown of asteroids by studying the multiscale mechanics of dynamic fracture and fragmentation, coupled with computational simulations of gravitational re-accumulation. The critical mechanisms are addressed through fundamental high-strain-rate experiments, high-speed visualization, theoretical and computational modeling of failure processes, and computational simulations of asteroid damage and disruption. Our focus is on the relative roles of impact and thermal loading on the nature of near-Earth asteroids (NEAs) that may potentially impact the Earth.