15,000 ‘City-Killer’ Asteroids Undetected: NASA Warning

No Way to Stop 15,000 ‘City-Killer’ Asteroids Yet: NASA Warns of Major Detection Gaps

Earth currently lacks a reliable system to detect and stop thousands of potentially catastrophic “city-killer” asteroids, according to NASA’s acting Planetary Defence Officer, Dr. Kelly Fast. Speaking at the American Association for the Advancement of Science (AAAS) conference in Phoenix, Arizona, she highlighted critical gaps in asteroid detection and tracking, raising concerns about planetary safety.

Scientists estimate that nearly 25,000 near-Earth asteroids measuring 140 meters or larger exist in space — large enough to cause massive regional destruction if they strike Earth. However, only about 40% of these objects have been identified, leaving nearly 15,000 dangerous asteroids untracked.

“What worries me most are the asteroids we don’t know about,” Dr. Fast said. While smaller objects usually burn up in the atmosphere and massive planet-killing asteroids are largely catalogued, mid-sized asteroids remain a major blind spot in planetary defense systems.

Why Mid-Sized Asteroids Are a Serious Threat

According to NASA, asteroids measuring 140 meters (460 feet) or more can cause devastating regional impacts, including large-scale destruction of cities, infrastructure collapse, massive fires, and long-term environmental damage. These asteroids are difficult to detect because many are dark, reflect very little sunlight, and often follow orbits similar to Earth’s, making them harder to spot using traditional telescopes.

The destructive potential of such objects was demonstrated during the 1908 Tunguska event in Siberia, when a space object exploded mid-air, flattening nearly 2,000 square kilometers of forest, despite being under 100 meters in size.

Limited Planetary Defense Capabilities

NASA and its global partners have tested asteroid deflection technologies, most notably the 2022 Double Asteroid Redirection Test (DART) mission. The mission successfully altered the orbit of a small asteroid’s moon by deliberately crashing a spacecraft into it — proving that asteroid deflection is possible.

However, experts emphasize that such missions require years of advance warning and highly specific conditions. Currently, no deflection spacecraft is on standby, and there is no rapid-response system in place if a dangerous asteroid is discovered with limited notice.

New Detection Efforts Underway

To close these detection gaps, NASA is developing the Near-Earth Object (NEO) Surveyor, an advanced infrared space telescope capable of spotting dark asteroids by detecting their heat signatures. This mission aims to help NASA meet its goal of identifying 90% of near-Earth asteroids larger than 140 meters within the next decade.

Additionally, ground-based observatories such as the Vera C. Rubin Observatory, along with international networks like the International Asteroid Warning Network (IAWN), are enhancing early-warning capabilities through global collaboration.

Final Outlook

While the chances of a large asteroid impact in the near future remain low, NASA officials stress that improved detection and tracking are essential to enable timely deflection missions. Until these technologies are fully operational, thousands of potentially dangerous asteroids remain hidden — posing a serious planetary risk.