What are asteroids? How real is the threat of them causing extinction of life? What strategies have been developed to prevent…

Asteroids are rocky, airless remnants left over from the formation of the solar system 4.6 billion years ago, mostly orbiting the Sun within the main asteroid belt between Mars and Jupiter; unlike icy comets or smaller pebble-to-boulder-sized meteoroids, they are composed primarily of minerals and metals.

Threat Assessment and Scientific Basis The threat of extinction-level impacts is statistically rare—occurring roughly every 50 to 100 million years—yet existential. The primary empirical evidence is the Cretaceous-Paleogene (K-T) mass extinction 66 million years ago, where a 10-kilometer asteroid struck the Chicxulub site, wiping out about 75% of species, including non-avian dinosaurs. Recent precedents like Tunguska (1908) and Chelyabinsk (2013) prove that even smaller Near-Earth Objects (NEOs) cause extensive atmospheric and surface damage. Scientists continuously evaluate these risks using the Torino and Palermo impact hazard scales to assess Potentially Hazardous Asteroids (PHAs). In 2025, asteroid 2024 YR4 briefly reached Torino level 3 before further observations ruled out an Earth impact.

Prevention Strategies Early detection and deflection form the two pillars of planetary defence:

• Detection and Tracking: Telescopic surveys like Spaceguard, Pan-STARRS, and ATLAS detect NEO trajectories. In India, ISRO monitors space hazards and NEOs through its Space Situational Awareness (SSA) Control Centre in Bengaluru.
• Mitigation Mechanisms: Proven methods include the Kinetic Impactor technique, demonstrated by NASA’s DART mission (2022), which altered the orbit of the asteroid Dimorphos; ESA's Hera mission (launched 2024, due to reach the Didymos system in late 2026) will measure the result in detail. Theoretical and developing techniques include Gravity Tractors for gradual gravitational towing, Laser Ablation to induce thrust via vaporisation, and stand-off Nuclear Deflection for large, short-warning objects.

A robust defence requires strengthening global coordination under the UN-endorsed International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG), eventually formalising an international treaty on planetary defence.