Planetary defense is the effort to monitor and protect Earth from asteroids, comets and other objects of threat in space. Read here to learn more.
According to NASA, Earth’s gravity pulls in over a hundred tonnes (more than 90 metric tonnes) of dust and tiny debris from space.
Larger pieces of this material may form a dazzling flash of light visible in the night sky or a tiny meteorite that a rock hunter may detect. However, most of this material burns away in the atmosphere without affecting the Earth.
There is less risk from these tiny encounters since Earth’s atmosphere is thicker and more shielding than that of Mercury or the moon, which have more exposed surfaces.
But asteroid impact has been recorded on Earth- The Chicxulub Crater is a large impact crater buried underneath the Yucatán Peninsula in Mexico. It is famously associated with the mass extinction event that led to the demise of the dinosaurs around 66 million years ago.
Planetary Defense
Planetary defense refers to the strategies and activities aimed at detecting, tracking, and mitigating the threat posed by near-Earth objects (NEOs), such as asteroids and comets, that could potentially collide with Earth and cause significant damage.
- Detection and Tracking:
- Numerous observatories and space agencies around the world conduct surveys to discover and monitor NEOs. Examples include NASA’s Near-Earth Object Observations Program and the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System).
- Creating and maintaining a comprehensive catalogue of NEOs to assess their orbits and potential impact risks.
- Characterization:
- Utilizing telescopes and radar to determine the size, shape, composition, and rotation of NEOs.
- Missions like NASA’s OSIRIS-REx and JAXA’s Hayabusa2, collect samples from asteroids to study their properties in detail.
- Impact Risk Assessment:
- Developing models to simulate potential impact scenarios and assess the effects of NEO collisions with Earth.
- Determining the likelihood of an NEO hitting Earth and the potential consequences of such an event.
- Mitigation Strategies:
- Various methods are being researched to alter the trajectory of an NEO. These include:
- Kinetic Impactor: A spacecraft that collides with an NEO to change its course (e.g., NASA’s DART mission).
- Gravity Tractor: A spacecraft that uses its gravitational attraction to slowly alter the NEO’s path.
- Nuclear Explosives: Using a nuclear explosion near the NEO to change its trajectory (considered a last-resort option).
- Breaking the NEO into smaller, less dangerous pieces, although this approach is less favoured due to the difficulty in controlling the fragments.
- Various methods are being researched to alter the trajectory of an NEO. These include:
Recent Missions
- DART Mission: Double Asteroid Redirection Test (DART) is NASA’s first mission to demonstrate a kinetic impactor technique to change the motion of an asteroid in space. The mission targeted the moonlet Dimorphos of the asteroid Didymos and successfully impacted it in September 2022.
- ESA’s Hera Mission: Hera is a European Space Agency (ESA) mission planned to follow up on the DART impact, providing detailed post-impact data on the deflection achieved and the physical properties of Dimorphos and Didymos.
- Planetary Defense Coordination Office (PDCO): Established by NASA in 2016, the PDCO is responsible for the coordination of efforts to detect, track, and characterize NEOs and for implementing strategies to mitigate the potential hazards they pose.
International Cooperation
Planetary defense is a global effort requiring collaboration among various countries and space agencies. Key international partners include:
- United Nations Office for Outer Space Affairs (UNOOSA): Facilitates international cooperation and coordination on planetary defense.
- International Asteroid Warning Network (IAWN): An international group of observatories and agencies sharing data and information on NEO threats.
- Space Mission Planning Advisory Group (SMPAG): An international forum for space agencies to plan and coordinate NEO impact mitigation missions.
Importance of Planetary Defense
- Preventing Catastrophic Impacts: Large NEO impacts can cause widespread destruction, loss of life, and long-term environmental damage. Effective planetary defense can prevent such disasters.
- Scientific Advancement: Studying NEOs enhances our understanding of the early solar system and the formation of planets.
- Global Security: International collaboration in planetary defense promotes global security and fosters cooperation in space exploration and research.
Why in the news?
The Indian Space Research Organization (ISRO) is keen on participating in a planetary defence mission in space ahead of a close shave for Earth with the Apophis asteroid on April 13, 2029, ISRO chairman S Somanath and senior scientists said at an international workshop held in Bengaluru to mark Asteroid Day 2024.
- Asteroid Day is observed every year by the space community on June 30 on account of a huge air blast from an asteroid flattening 2,200 sq km of forest in Siberia, Russia, on June 30, 1908.
- Asteroids are hypothesized to have caused the extinction of dinosaurs.
Asteroid Apophis
99942 Apophis is an asteroid that gained significant attention due to its close approach to Earth and the initial concern about its potential impact.
Discovered on June 19, 2004, by astronomers Roy A. Tucker, David J. Tholen, and Fabrizio Bernardi, Apophis is named after the Egyptian god of chaos.
- Size: Approximately 370 meters in diameter.
- Orbit: Apophis orbits the Sun and crosses Earth’s orbit, classifying it as a Near-Earth Object (NEO).
- Composition: Like many asteroids, it is likely composed of rock, metal, and other materials.
- 2029 Close Approach: On April 13, 2029, Apophis will pass very close to Earth, within approximately 31,000 kilometres (19,000 miles). This distance is closer than some of Earth’s satellites. This encounter will provide a unique opportunity for scientists to study the asteroid up close using ground-based observations.
- 2036 Close Approach: Initially, there were concerns about a potential impact in 2036. However, continued observations and refined orbital calculations have effectively ruled out this possibility.
Risk Assessment and Monitoring
- When first discovered, there was significant concern that Apophis might collide with Earth in 2029 or 2036. Initial calculations suggested a relatively high probability of impact, which has since been drastically reduced with more accurate data.
- As of recent observations, the likelihood of Apophis impacting Earth in the foreseeable future is extremely low. NASA and other space agencies continue to monitor its trajectory closely.
Scientific Significance
- Study of Near-Earth Objects (NEOs): Apophis provides a valuable opportunity to study NEOs, improving our understanding of their orbits, compositions, and potential threats.
- Planetary Defense: The close approach of Apophis has spurred interest in planetary defense strategies, including potential deflection techniques to protect Earth from future asteroid impacts.
The close approach in 2029 will allow for extensive observations using radar and optical telescopes.
Scientists aim to gather data on Apophis’s shape, rotation, surface properties, and any potential changes in its orbit due to Earth’s gravitational influence.
Conclusion
Planetary defense is a critical aspect of space science and global security, aimed at protecting Earth from potential asteroid and comet impacts.
Through detection, tracking, characterization, and mitigation strategies, along with international cooperation, humanity can prepare for and prevent possible NEO threats.
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-Article by Swathi Satish
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