Planetary Defense Today

Earth has been struck by asteroids throughout its history, and the threat continues. NASA's Planetary Defense Coordination Office tracks known near-Earth objects and calculates their future orbits, and over 2,300 potentially hazardous asteroids have been cataloged so far.

The DART mission showed in 2022 that a kinetic impactor can shift an asteroid's orbit, and ESA's Hera mission is en route to survey the impact site up close after its scheduled arrival at Didymos/Dimorphos in late 2026. Future options being studied include gravity tractors, laser ablation, and nuclear deflection for larger threats. For the first time, we have early tools to redirect an asteroid rather than simply watch it come.