What are asteroids? How real is the threat of them causing extinction of life? What strategies have been developed to prevent such a catastrophe? (Answer in 250 words)

Introduction

Asteroids are rocky remnants orbiting the Sun; most are harmless, but near-Earth objects can cause regional or global devastation.

Threat assessment

• Large impacts are rare but capable of fires, tsunamis, dust-induced cooling and food-system collapse; smaller airbursts can still damage cities.
• Risk depends on size, composition, orbit, impact probability and warning time.

Prevention

• Global sky surveys, radar and space-based observation improve detection and orbit calculation.
• NASA’s DART demonstrated kinetic-impact deflection; future options include gravity tractors, reconnaissance and, only as a last resort, nuclear disruption.
• International notification, civil-defence planning and planetary-defence coordination are essential because prevention is global public security.

Keywords: NEO, impact probability, DART, kinetic impactor, planetary defence.