Tiny Asteroids, Big Threats: JWST Reveals a Hidden World of Mini Asteroids

One significant threat to life here on Earth is the possibility that a massive asteroid will collide with our planet and destroy life as we know it. To understand the possibilities, large surveys of the sky have found around 95% of potentially hazardous asteroids larger than a kilometer. Smaller asteroids, however, can also cause massive amounts of damage. Estimates range from 40 to 60 percent when it comes to asteroids over 100 meters in diameter, which would be considered city-killers. Even smaller asteroids, such as the 20-meter one that exploded over Chelyabinsk in 2013, can cause destruction and injury. The more asteroids we can find, the better our predictions and future protections will be. In light of this threat, scientists have used the JWST to detect 138 of the smallest asteroids (as small as 10 meters) ever observed in the asteroid belt. These tiny asteroids are important because they can become near-Earth objects (NEOs), posing a risk to Earth through possible impacts, including powerful explosions. By analyzing the size and frequency of asteroids, researchers found a significant change in the population of asteroids around 100 meters in size, likely due to collisions breaking larger asteroids into smaller ones. The observed asteroids originated from known asteroid families and were detected using advanced tracking and infrared imaging techniques. This research enhances our understanding of asteroid behavior and may aid in predicting and mitigating future asteroid threats. Join planetary astronomer Franck Marchis in a conversation with lead authors Artem Y. Burdanov and Julien de Wit as they discuss these smaller asteroids and what they can reveal about potential threats to our planet. (Recorded live 1 May 2025.)