NASA Warns of 15,000 Undetected Asteroids Posing a Threat to Earth
The potential for a devastating asteroid impact, once relegated to the realm of science fiction, is receiving renewed attention from planetary scientists. Recent data presented by NASA’s acting planetary defense officer, Kelly Fast, reveals a sobering reality: approximately 15,000 near-Earth asteroids larger than 140 meters (460 feet) in diameter remain undetected. These “city-killer” asteroids, whereas not representing an immediate threat, pose a significant long-term risk due to their potential to cause regional devastation upon impact. The revelation underscores a critical gap in current planetary defense capabilities and highlights the urgent need for improved surveillance infrastructure. This isn’t a matter of if, but when, according to experts and the current state of detection leaves a considerable margin for dangerous uncertainty.
Fast presented these findings on February 14, 2026, at the American Association for the Advancement of Science annual meeting in Phoenix, Arizona. The discrepancy between estimated and detected asteroid populations is a persistent concern for NASA, and Fast described the situation as something that “keeps me up at night,” emphasizing the gravity of the situation. The agency’s models, refined over decades of observation, estimate a total population of roughly 25,000 near-Earth asteroids exceeding 140 meters in diameter. Although, current surveys have only cataloged approximately 10,000, leaving a substantial portion of these potentially hazardous objects unfound. The challenge lies not in the absence of asteroids, but in our inability to locate them.
The Scale of the Threat: What are “City-Killer” Asteroids?
Asteroids larger than 140 meters are classified as potentially hazardous objects (PHOs) due to their capacity to inflict significant damage. While smaller asteroids burn up in the Earth’s atmosphere, creating spectacular meteor showers, larger asteroids can survive the descent and impact the surface. An asteroid of this size impacting a populated area could level a city, triggering widespread destruction, tsunamis (if impacting the ocean), and potentially causing global climate disruption. The energy released from such an impact would be equivalent to multiple megatons of TNT. NASA’s Eyes on Asteroids provides a valuable interactive tool for visualizing the orbits of known asteroids and understanding the potential risks.
The 15,000 undetected asteroids aren’t speculative threats; they are statistical inferences derived from observational astronomy and sampling methodologies. Researchers know these objects exist based on modeling, but their precise locations remain unknown. This gap between statistical prediction and observational reality defines the current state of planetary defense. The size of these asteroids is particularly concerning. They are large enough to cause serious damage, but small enough to avoid easy detection by current telescopes and survey programs. The challenge is compounded by the fact that many of these asteroids have orbits that take them closer to the sun, making them tricky to observe against the glare of the sun.
Current Detection Efforts and Limitations
NASA and other space agencies around the world are actively engaged in identifying and tracking near-Earth objects (NEOs). These efforts include ground-based telescopes, such as the Pan-STARRS and Catalina Sky Survey, as well as space-based observatories like the Near-Earth Object Surveyor (NEO Surveyor), which is currently under development. The NEO Surveyor mission, slated for launch in the coming years, is designed to significantly enhance our ability to detect and characterize potentially hazardous asteroids. However, even with these advancements, a substantial portion of the asteroid population will remain hidden from view for the foreseeable future.
The limitations of current detection methods stem from several factors. Firstly, the vastness of space makes it challenging to scan the entire sky effectively. Secondly, many asteroids have dark surfaces, making them difficult to detect even with powerful telescopes. Thirdly, the orbits of asteroids are constantly changing due to gravitational interactions with planets, making it necessary to continuously update tracking data. Finally, funding constraints and competing priorities can limit the resources available for asteroid detection and mitigation efforts. As Fast explained to the Daily Star, “It’s estimated We find about 25,000 of those, and we’re only about 40 percent of the way through. It takes time to find them, even with the best telescopes.”
The Role of the NEO Surveyor Mission
The upcoming launch of the NEO Surveyor is a critical step in bolstering planetary defense. This space-based infrared telescope is specifically designed to detect and track NEOs, including those that are difficult to observe from the ground. By operating from space, NEO Surveyor will avoid the atmospheric distortions that limit the performance of ground-based telescopes and will be able to scan a larger portion of the sky more efficiently. The mission is expected to discover and characterize a significant fraction of the remaining undetected asteroid population, providing valuable data for assessing and mitigating the risk of impact. MSN News reports that the mission is a key component of NASA’s overall planetary defense strategy.
What Happens When an Asteroid is Detected?
Once a potentially hazardous asteroid is detected, NASA and other international organizations begin to track its orbit and assess the risk of impact. This involves making precise measurements of the asteroid’s position and velocity over time. The data is then used to refine the asteroid’s orbit and predict its future trajectory. If the calculations indicate a significant probability of impact, mitigation strategies are considered. These strategies could include deflecting the asteroid using a kinetic impactor (essentially ramming a spacecraft into the asteroid to alter its course) or using a gravity tractor (a spacecraft that uses its gravitational pull to slowly nudge the asteroid off course). The Double Asteroid Redirection Test (DART) mission, which successfully impacted the asteroid Dimorphos in 2022, demonstrated the feasibility of the kinetic impactor technique.
However, it’s essential to note that deflecting an asteroid is a complex and challenging undertaking. It requires years of advance warning and precise calculations to ensure that the deflection is successful and does not inadvertently increase the risk of impact. The effectiveness of different deflection techniques depends on the size, composition, and orbit of the asteroid. Currently, no asteroid poses an imminent threat to Earth, but the discovery of a potentially hazardous object with a short warning time could necessitate a rapid response.
International Collaboration in Planetary Defense
Planetary defense is a global effort that requires international collaboration. NASA works closely with space agencies around the world, including the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA), and others, to share data, coordinate observations, and develop mitigation strategies. The International Asteroid Warning Network (IAWN) serves as a central hub for sharing information about NEOs and coordinating response efforts. This collaborative approach is essential for ensuring that all of humanity is protected from the threat of asteroid impact.
Key Takeaways
- Approximately 15,000 near-Earth asteroids larger than 140 meters remain undetected, posing a potential threat to Earth.
- These “city-killer” asteroids could cause regional devastation upon impact.
- NASA’s NEO Surveyor mission is designed to significantly improve our ability to detect and track NEOs.
- Planetary defense is a global effort that requires international collaboration.
- While no asteroid currently poses an imminent threat, continued vigilance and investment in planetary defense are crucial.
The ongoing efforts to identify and track near-Earth asteroids represent a vital investment in the long-term safety of our planet. As technology advances and our understanding of the asteroid population improves, we will be better equipped to mitigate the risk of impact and protect future generations. The next major milestone in this endeavor will be the launch of the NEO Surveyor mission, which is expected to provide a more complete picture of the asteroid population and enhance our ability to respond to potential threats. Readers are encouraged to follow updates from NASA and the International Asteroid Warning Network for the latest information on this critical issue. Share your thoughts and concerns in the comments below.