Planetary defence, which focuses on detecting and tracking asteroids and comets that could endanger Earth, gained prominence after events such as the 1908 Tunguska explosion in Siberia, which flattened 2,000 square kilometres of forest, and the formation of Meteor Crater in Arizona, created by an impact 50,000 years ago. For much of human history, the chances of saving Earth from an asteroid strike seemed almost unimaginable. Today, however, space scientists are increasingly confident in their ability to safeguard the planet, thanks to a coordinated global effort involving some of the world’s leading space agencies. From Japan to India, Europe to the United States, scientists are actively tracking, studying and working to deflect near-Earth objects (NEOs) that could pose a threat.
One of the major players in this field is the Japan’s space agency JAXA. Its two asteroid missions, Hayabusa and Hayabusa2, demonstrated that it was possible to collect samples from asteroids and bring them safely to Earth. Makoto Yoshikawa, the scientist behind both missions, told THE WEEK that while collisions with celestial bodies were rare, the damage they could cause was considerable. “That is why JAXA continues to send spacecraft to study near-Earth asteroids,” he said. “We have also developed a special technique called ‘stacking’ to detect and observe asteroids. Using small telescopes, we can identify small, fast-moving asteroids.”
Hayabusa2 is now on an extended mission, with a flyby of asteroid 98943 Torifune scheduled for July next year. This will be followed by a rendezvous with asteroid 1998 KY26 in 2031. These smaller, more frequent asteroids are harder to detect, yet potentially more dangerous.
JAXA is also contributing to the European Space Agency’s (ESA) Hera mission, which launched aboard a SpaceX Falcon 9 last October. “We provided Hera with a thermal infrared camera,” said Yoshikawa. Hera’s primary mission is to study the Didymos–Dimorphos binary asteroid system, where it will arrive in December 2026. The mission will study the impact site created on Dimorphos by NASA’s DART (Double Asteroid Redirection Test, which successfully struck the asteroid in 2022) and analyse the asteroid’s internal structure to refine deflection techniques. JAXA also operates the Bisei Space Guard Centre that tracks asteroids and space debris, and collaborates with organisations like the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG).
India has also stepped up its planetary defence activities. “Asteroids will not strike like missiles or lasers, but they can hit us and cause significant destruction,” said S. Somanath, former chairman of the Indian Space Research Organisation. “As a spacefaring nation, India must be ready. We must engage in discussions and plan for Earth’s protection.”
ISRO, while yet to launch a dedicated planetary defence mission, monitors NEOs through its network of ground-based observatories and satellite assets. It also participates in international frameworks such as IAWN and SMPAG, signalling its commitment to global efforts. One key area of focus for India is the observation of asteroid 99942 Apophis, which will pass Earth at a distance of just 32,000km on April 13, 2029. India’s tracking of this event reflects its growing interest in both planetary defence and the protection of its expanding space infrastructure. ISRO’s missions, including Chandrayaan and Mangalyaan, have contributed valuable scientific data on celestial bodies. Its solar mission, Aditya-L1, aims to study how solar radiation and wind affect the orbits of asteroids and comets, improving trajectory predictions.
The ESA is developing the RAMSES (Rapid Apophis Mission for Space Safety) mission, which could launch in April 2028 to intercept Apophis before its 2029 flyby, aiming to study the asteroid’s surface and monitor its response to Earth’s gravitational pull. NASA, meanwhile, continues to lead global efforts with its Planetary Defence Coordination Office (PDCO), established in 2016 to oversee asteroid detection, tracking and risk assessment. Its upcoming mission, the NEO Surveyor, is an infrared space telescope designed to identify most potentially hazardous NEOs within 50 million kilometres of Earth.
NASA’s DART mission marked the first real-world test of kinetic impact as a deflection method. “That mission proved that we can shift a smaller asteroid’s path if it poses a risk,” said Annapurni Subramaniam, director of the Indian Institute of Astrophysics (IIA). “There are many options under consideration for dealing with such threats.” She also warned against outdated notions of destroying asteroids with explosives. “The idea of blowing up an asteroid has fallen out of favour. A better method is to gently deflect it by crashing a spacecraft into it. But the first step in any defence strategy is to map and monitor nearby space rocks, then identify those likely to come close, such as Apophis. Depending on their size and trajectory, we can then prepare a targeted response. This must be a global effort.” A 70cm telescope at the Indian Astronomical Observatory at Hanle in southeastern Ladakh has been involved in identifying NEOs. “Once a potentially hazardous asteroid is detected, the next step is to accurately calculate its orbit and, if necessary, develop a strategy to alter it,” said Subramaniam.
The upcoming flyby of Apophis is expected to be one of the most closely monitored planetary defence events. Observations from ground telescopes, radar systems and spacecraft will help scientists refine orbital models and assess how Earth’s gravity could affect the asteroid’s structure. Srimathy Kesan, founder and CEO of Space Kidz India, said the potential impact of an asteroid like Apophis could be devastating. “The energy released would be equivalent to hundreds of megatons of TNT, causing massive destruction and loss of life,” Kesan said. “This highlights the need for continued investment in planetary defence technologies and international cooperation.”