NASA's Kelly Fast Highlights Risks from Undetected Mid-Sized Asteroids

NASA's planetary defense officer, Kelly Fast, has expressed concern over the threat posed by undetected mid-sized asteroids, often referred to as 'city-killers.' These asteroids, approximately 500 feet in diameter, are large enough to cause significant regional damage upon impact but small enough to evade current detection methods. Fast highlighted that while larger asteroids are well-tracked and smaller ones pose minimal risk, these mid-sized objects remain elusive.

According to Fast, there are about 25,000 such near-Earth objects, with only 40% currently identified. Their detection is complicated by their size and the fact that they often follow Earth's orbit around the Sun, making them difficult to spot with existing telescopes. To address this gap, NASA plans to launch the Near-Earth Object Surveyor (NEO Surveyor) space telescope no earlier than September 2027. This infrared telescope is designed to detect both bright and dark asteroids by capturing their thermal signatures, thereby improving the identification of previously hidden objects.

Despite advancements in detection, current capabilities to actively deflect such asteroids are limited. Nancy Chabot, leader of NASA's Double Asteroid Redirection Test (DART), noted that while the 2022 DART mission demonstrated the ability to alter an asteroid's trajectory by crashing a spacecraft into it, replicating such a mission for a 'city-killer' asteroid would be challenging due to the lack of ready-to-deploy deflector crafts. Chabot emphasized the need for increased investment in planetary defense measures to prepare for potential future threats.