NASA Asteroid Warning: Thousands of ‘City Killer’ Space Rocks Remain Undetected
Humanity faces a growing, yet largely unseen, threat from space. NASA officials have cautioned that thousands of medium-sized asteroids – dubbed “city killers” – are currently passing near Earth, and a significant portion remain undetected. Estimates suggest around 15,000 of these space rocks are lurking in the darkness, potentially on a collision course with our planet.
While NASA’s successful Double Asteroid Redirection Test (DART) in 2022 demonstrated our capability to alter an asteroid’s trajectory, the mission’s own chief, Dr. Nancy Chabot of Johns Hopkins University, emphasizes that we lack a readily available system for immediate response. “DART was a great demonstration, but we don’t have that sitting around ready to go if there was a threat we needed to use it for,” she stated. “It would be a catastrophe if certain-sized asteroids hit us.”
The primary concern lies with asteroids approximately 140 meters in diameter. Dr. Chabot highlights that we currently only know the location of about half of these potentially dangerous objects. “We don’t know where 50% of the 140-metre asteroids are, which is a concern. We would not have any way to go and actively deflect one right now.” She further notes a lack of investment in maintaining planetary defense systems on standby.
Dr. Kelly Fast, NASA’s Planetary Defense Officer, echoed these concerns, stating that mid-sized asteroids are her biggest worry. Speaking at the American Association for the Advancement of Science (AAAS) conference, she explained, “What keeps me up at night is the asteroids we don’t know about… It’s the ones in between, about 140 metres and larger, that could really do regional rather than global damage and we don’t know where they are.” It’s estimated that around 25,000 asteroids of this size exist, and we’ve only identified approximately 40% of them. The process of discovery is time-consuming, even with advanced telescopes.
New Comet on the Horizon
Adding to the celestial activity, a newly discovered comet, C/2024 E1 (Wierzchoś), is rapidly approaching Earth. Discovered in March 2024 by Polish astronomer Kacper Wierzchoś, this comet is estimated to be around 8.5 miles (13.7 km) in diameter – roughly two-thirds the length of Manhattan. This interstellar visitor is brightening as it nears its closest point to Earth on Tuesday.
Scientists predict that Comet Wierzchoś could take decades or even centuries to fully leave our solar system. Once it does, it will embark on a journey spanning billions of years, potentially passing through other star systems in the Milky Way galaxy. You can find more information about comets and asteroids at NASA’s Planetary Defense Coordination Office.
The ongoing search for near-Earth objects (NEOs) is crucial for planetary defense. Continued investment in detection and deflection technologies is essential to mitigate the risk posed by these celestial threats. Space.com provides further insights into asteroid defense strategies.
