Q.16. What are asteroids? How real is the threat of them causing extinction of life? What strategies have been developed to prevent such catastrophe? [UPSC 2024 GS P-3]

What are Asteroids?

Asteroids are small, rocky objects that orbit the Sun, primarily found in the Asteroid Belt between Mars and Jupiter. They range in size from a few meters to hundreds of kilometers in diameter and are remnants from the early solar system that never formed into planets. Some asteroids have orbits that bring them close to Earth, known as Near-Earth Objects (NEOs).

Threat of Extinction from Asteroids

The possibility of an asteroid causing mass extinction is real but rare. The most famous example of such an event is the Chicxulub asteroid impact, which is widely believed to have caused the extinction of the dinosaurs around 66 million years ago. This event released an immense amount of energy, causing fires, tsunamis, and long-term climate disruptions, wiping out about 75% of life on Earth.

Though impacts of this magnitude are rare, smaller asteroids still pose a significant threat. For instance:

• Tunguska Event (1908): A small asteroid (or comet) exploded over Siberia, flattening over 2,000 square kilometers of forest.
• Chelyabinsk Meteor (2013): An asteroid exploded over Russia, injuring over 1,500 people and damaging buildings due to the shockwave.

The NASA Sentry system tracks over 30,000 known NEOs, and while the majority do not pose an immediate threat, it’s estimated that we have detected less than half of NEOs larger than 140 meters, which could cause significant regional damage if they struck Earth.

Strategies to Prevent an Asteroid Catastrophe

Several strategies have been developed to prevent an asteroid impact:

1. Detection and Monitoring:
   • NASA’s Planetary Defense Coordination Office (PDCO) tracks and monitors potentially hazardous asteroids. The aim is to detect asteroids early enough to devise a mitigation strategy.
   • Telescopes such as Pan-STARRS and the NEOWISE mission are dedicated to discovering and tracking NEOs, with plans for improved systems like the Near-Earth Object Surveyor.
2. Deflection Missions:
   • The idea is to change an asteroid’s orbit so it avoids Earth. Several methods are being researched:
     • Kinetic Impactor: A spacecraft would crash into the asteroid to change its velocity. NASA’s DART (Double Asteroid Redirection Test) mission successfully tested this in 2022, altering the orbit of a small asteroid (Dimorphos).
     • Gravity Tractor: A spacecraft would fly close to an asteroid and use its gravitational pull to slowly change the asteroid’s path over time.
3. Nuclear Explosions:
   • In extreme cases, a nuclear explosion could be used to either disrupt or deflect an asteroid. The aim would be to alter its trajectory or break it into smaller pieces that would burn up in Earth’s atmosphere.
   • This method is considered risky due to the unpredictability of the fragmentation and fallout.
4. Evacuation and Damage Mitigation:
   • If an impact cannot be avoided, early detection would allow for evacuation of the impact zone. Governments could also prepare by reinforcing critical infrastructure against blast waves or tsunamis.

Conclusion

The threat of an asteroid causing a mass extinction is real, but extremely rare. Ongoing efforts to detect, track, and develop mitigation strategies are essential to protect the Earth. While technologies like the DART mission show promise, continued investment in planetary defense systems is critical to prevent a potential catastrophe.