Asteroids are essentially rocky, airless remnants left over from the early formation of our solar system, about 4.6 billion years ago. They vary widely in size, from small pebbles to minor planets hundreds of kilometers in diameter, and orbit the Sun, primarily concentrated in the asteroid belt between Mars and Jupiter. However, some have orbits that bring them close to Earth, making them "Near-Earth Objects" (NEOs).

The threat of an asteroid causing extinction of life is a real, albeit low-probability, concern. History bears witness to such an event; the Chicxulub impact 66 million years ago, believed to have been caused by a roughly 10-kilometer wide asteroid, led to the extinction of dinosaurs and widespread global devastation. While smaller asteroids (tens to hundreds of meters) hit Earth more frequently, like the Tunguska event or the Chelyabinsk meteor, these typically cause regional rather than global catastrophes. An extinction-level event from a large asteroid is exceedingly rare, occurring perhaps once every tens to hundreds of millions of years, but its potential impact necessitates preparedness.

Fortunately, several strategies have been developed to prevent such a catastrophe, primarily focusing on early detection and deflection. The first crucial step is detection and tracking: observatories worldwide, including NASA's Planetary Defense Coordination Office, continuously survey the skies to identify and track NEOs, calculating their trajectories and potential impact risks well in advance.

If a potentially hazardous asteroid is detected early enough, deflection methods can be employed. The most promising current strategy is the Kinetic Impactor, where a spacecraft is deliberately crashed into the asteroid to alter its velocity and trajectory, nudging it off its collision course with Earth. NASA's DART (Double Asteroid Redirection Test) mission successfully demonstrated this in 2022. Other theoretical strategies include the Gravity Tractor, where a spacecraft flies alongside an asteroid, using its tiny gravitational pull to gently tug the asteroid off course over time. Less preferred, but considered a last resort, would be a nuclear detonation near or on the asteroid to either shatter it or push it away, though this carries significant risks. The key to all these strategies is early warning – the more time we have, the more effective and less drastic the intervention can be.