Full Breakdown
NASA's Ongoing Challenge with Undetected 'City-Killer' Asteroids
2/17/2026, 1:22:46 AM
The Threat of Undetected Asteroids
NASA's head of planetary defense, Dr. Kelly Fast, has raised concerns about the tens of thousands of mid-sized asteroids, referred to as "city-killers," that remain undetected. These asteroids, defined as being at least 140 meters in diameter, pose a significant risk of causing regional damage if they were to impact populated areas on Earth. Currently, approximately 15,000 of these asteroids are unaccounted for, raising alarms within the scientific community about the potential for catastrophic events.
Recent Developments in Planetary Defense
In 2022, NASA successfully executed the Double Asteroid Redirection Test (DART) mission, which involved crashing a spacecraft into the mini-moon Dimorphos at a speed of 14,000 mph to alter its orbit. This mission was a pivotal demonstration of the potential to deflect incoming asteroids. However, Dr. Nancy Chabot, a planetary scientist at Johns Hopkins University and leader of the DART mission, noted that there are currently no additional spacecraft ready for immediate deployment should a threatening asteroid be detected.
The asteroid YR4, measuring up to 90 meters wide, was previously identified with a 3.2% chance of hitting Earth in 2032, although this risk was later downgraded to zero. Dr. Chabot emphasized that if a similar threat were to arise, there would be no active means to deflect it, highlighting a critical gap in current planetary defense capabilities.
NASA's Detection Efforts
During a discussion at the American Association for the Advancement of Science (AAAS) conference in Phoenix, Dr. Fast explained that while larger asteroids are easier to detect, only about 40% of mid-sized asteroids have been identified so far. This lack of knowledge about the whereabouts of these asteroids is concerning, as Dr. Fast stated, "It's really the asteroids that we don't know about" that pose the greatest risk.
To address this issue, NASA has been tasked by the U.S. Congress with locating over 90% of near-Earth objects larger than 140 meters. The agency is currently developing the Near-Earth Object (NEO) Surveyor mission, which is expected to launch next year. This space telescope aims to detect both bright and dark asteroids, including those that are particularly challenging to find.
Criticism and Future Directions
Despite the advancements made through the DART mission and ongoing detection efforts, experts like Dr. Fast and Dr. Chabot express concern over the lack of immediate defensive measures against potential asteroid threats. Dr. Fast concluded, "We're searching skies to find asteroids before they find us, and get them before they get us," underscoring the urgency of investing in planetary defense technologies.
Conflicting Reports & Gaps
While NASA has made strides in asteroid detection and deflection, the acknowledgment of thousands of undetected mid-sized asteroids raises questions about the effectiveness of current strategies. The scientific community continues to call for increased investment and resources to enhance planetary defense capabilities.
Verbatim Quotes
- "It's really the asteroids that we don't know about." — Dr. Kelly Fast, Head of Planetary Defense, NASA
- "DART was a great demonstration, but we don't have [another] sitting around ready to go if there was a threat that we needed to use it for." — Dr. Nancy Chabot, Planetary Scientist, Johns Hopkins University
- "We're searching skies to find asteroids before they find us, and get them before they get us." — Dr. Kelly Fast, Head of Planetary Defense, NASA
