The Earth faces many natural threats, but among them, asteroid impacts stand out for their potential to cause massive destruction.
Planetary Defence: A Preventable Natural Disaster
From minor atmospheric burnouts to extinction-level events, the danger depends on the size and speed of the celestial body. While such catastrophic events are rare, the possibility is very real—one that scientists take seriously due to evidence of past impacts seen in craters around the globe.
Fortunately, planetary defence is a unique kind of natural threat—it’s the only one that science can actively try to prevent. Unlike earthquakes or hurricanes, humans have developed technology that can detect and even deflect threatening space objects before they reach Earth. This effort is led not by military powers, but by space agencies like NASA and the European Space Agency (ESA), which are actively monitoring and preparing for potential asteroid threats.
While many defence alliances and countries—such as NATO and its member nations—operate advanced space monitoring systems, their focus is on military threats. This includes the tracking of ballistic missiles, spy satellites, and other military objects in low and medium Earth orbit. Their missions primarily concentrate on the land, air, sea, cyber, and near-Earth space domains. Beyond geostationary orbit, which is about 36,000 kilometers from Earth, military interest fades, and scientific agencies step in to manage planetary defence operations.
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NASA and ESA Step Up for Earth’s Protection
NASA and ESA have taken the lead in the defence of the planet from potential asteroid collisions. In 2016, NASA created the Planetary Defense Coordination Office to detect and monitor near-Earth objects (NEOs) that could pose a risk. ESA had already established a similar planetary defence centre in 2013. These agencies work alongside international networks like the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG), both affiliated with the United Nations, to strengthen global defence strategies against celestial threats.
One of the most talked-about defence projects was NASA’s DART mission, which launched a spacecraft in 2022 to crash into an asteroid called Dimorphos. This asteroid was about 163 meters wide—bigger than a football field—and the goal was to see if its path could be changed. The test was successful. The collision altered the asteroid’s orbit, proving that defence through deflection is possible.
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Following that, ESA launched its Hera mission to study Dimorphos in more detail. The spacecraft, weighing over 800 kilograms, is now on its way to the asteroid and is expected to reach it by late 2026. Scientists aim to measure the changes caused by the DART impact and ensure the asteroid did not break into multiple fragments, which would have made the threat worse. The goal is always to deflect, not destroy, as part of responsible planetary defence planning.
Besides direct impact, another method being studied involves ion beam technology. This method sends a slow but steady ion beam at an asteroid to gently push it off course. It’s a controlled way to change the object’s path without breaking it. However, this method only works if the object is detected many years in advance—ideally more than 15 years before potential impact.
What We Know About the Asteroid Population
Space agencies have been tracking a wide range of near-Earth objects—rocky fragments left over from the formation of the solar system around 4.6 billion years ago. Most of these space rocks are very small, under 10 meters in size. They pose minimal risk since they usually burn up in the Earth’s atmosphere. NASA estimates there are around 45 million of these tiny objects.
More concerning are the larger asteroids. As of June this year, 38,612 near-Earth objects larger than 10 meters have been recorded. Among them, 872 are over one kilometer wide—big enough to cause global disaster. About 50 more are believed to be out there, still undiscovered.
There are also over 11,000 asteroids that measure around 140 meters—comparable in size to the Great Pyramid of Giza. Scientists estimate around 14,000 more of these could exist. Even smaller ones, around 50 meters, could cause regional devastation. Only about 10% of these have been found.
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For asteroids under 500 meters in size, current technology—like kinetic impactors—is often enough to change their path. But for larger objects, more force may be needed. In such cases, scientists have suggested using nuclear devices, though this option is controversial. It is seen as a last resort and would require international approval. However, such a step has not yet been necessary.
Despite military interest in space, planetary defence remains in the hands of space scientists. No military alliance, not even NATO, has taken direct responsibility for defending Earth from asteroids. Instead, international coordination through civilian agencies continues to play the leading role in protecting the planet from threats that come from the vastness of space.
