The Asteroid Belt

Between Mars and Jupiter lies the asteroid belt, home to millions of rocky bodies. Despite what movies suggest, the belt is mostly empty space — spacecraft pass through without dodging anything. The largest object is Ceres, a dwarf planet 940 km across that holds about a third of the belt's total mass.

Near-Earth asteroids are a different concern. Thousands of them cross Earth's orbit, and the one that killed the dinosaurs 66 million years ago was roughly 10 km wide. In 2022, NASA's DART mission nudged a small asteroid's orbit — the first real test of whether we could one day steer a dangerous one away.