The National Aeronautics and Space Administration (NASA) has issued a stark warning about 15,000 “city-killer” asteroids that could strike Earth at any time, highlighting a significant gap in global planetary defense capabilities. These mid-sized rocks, approximately 140 meters in diameter, are large enough to cause regional destruction but remain difficult to monitor with existing tools.
Kelly Fast, NASA’s acting planetary defense officer, explained at the American Association for the Advancement of Sciences in Phoenix that impacts from these asteroids could devastate populated regions, potentially destroying cities and critical infrastructure. She emphasized that Earth currently lacks effective defenses against this particular class of asteroids, making early detection and mitigation essential.
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Unlike the largest asteroids, which can cause global catastrophe and are closely tracked using specialized telescopes, these mid-sized rocks often evade monitoring due to their smaller size and unpredictable orbits. Fast noted that discovering them takes considerable time, even with the best observational technology currently available.
The warning follows heightened concern after comet 3I/ATLAS kept astronauts and scientists on edge throughout 2025. Similarly, the asteroid YR4, roughly the size of a football pitch, raised alarms last year, and although it passed safely, its orbit suggests it could return near the Moon and Earth system by 2032.
Nancy Chabot, DART mission chief at Johns Hopkins University, urged that global investment in asteroid detection and mitigation strategies remains insufficient. She stressed that without serious funding and international coordination, the world remains highly vulnerable to sudden asteroid impacts capable of regional devastation.
Experts warn that 2026 could be a critical year for planetary defense planning, as advances in telescopic monitoring, AI-assisted tracking, and international collaboration may be the only tools capable of preventing potential disasters. Swift action is needed to safeguard human populations from these hidden cosmic threats.