What would happen if a kilometer-diameter asteroid hit Earth, and how are scientists working to prevent such catastrophic impacts?

A kilometer-diameter asteroid impact would likely end human civilization by causing truly global devastation and potential extinction events. These massive objects pose an existential threat due to their ability to create worldwide catastrophic effects that could wipe out entire species. To address this threat, NASA and the global astronomical community have established planetary defense programs focused on discovering and tracking potentially hazardous objects (PHOs). While significant progress has been made in locating larger asteroids, ongoing international cooperation and preparedness efforts are essential to protect humanity from future asteroid impacts.