NASA’s asteroid-deflecting DART spacecraft nears its target

Ten months after launch, NASA's asteroid-deflecting DART spacecraft neared a planned impact with its target on Monday in a test of the world's first planetary defense system, designed to prevent a doomsday collision with Earth. Dimorphos and Didymos are both tiny compared with the cataclysmic Chicxulub asteroid that struck Earth some 66 million years ago, wiping out about three-quarters of the world's plant and animal species including the dinosaurs. Smaller asteroids are far more common and pose a greater theoretical concern in the near term, making the Didymos pair suitable test subjects for their size, according to NASA scientists and planetary defense experts. DART is the latest of several NASA missions in recent years to explore and interact with asteroids, primordial rocky remnants from the solar system's formation more than 4.5 billion years ago.