Each year, according to NASA, a car-sized asteroid hurtles toward Earth. Thanks to the planet’s atmosphere, most of these objects burn up upon entry, producing dazzling meteor showers. However, larger asteroids present a much more serious threat, with the potential to cause widespread devastation.
Asteroids come in all sizes, with some massive enough to cause global extinction events. Michael Küppers, a planetary scientist at the European Space Agency (ESA), points to the asteroid believed to have wiped out the dinosaurs—measuring around 10 kilometers wide—as an example of the catastrophic impact these space rocks can have. Such colossal collisions occur approximately once every 100 million years, according to experts.
The Asteroid Making Headlines: 2024 YR4
A newly discovered asteroid, 2024 YR4, has captured international attention. Found in December 2024, YR4 is estimated to be between 40 and 90 meters wide, potentially larger than a 12-story building. In January 2025, ESA initially calculated a 1.2% chance of the asteroid impacting Earth on December 22, 2032, surpassing the 1% risk threshold that triggers further investigation by planetary defense organizations and even political leaders, including the U.S. President and Congress.
Although YR4 is not large enough to cause global extinction, it has been classified as a possible “city killer”—capable of devastating an urban area if it were to hit a densely populated region. In February 2025, concerns briefly heightened as impact odds climbed to 3.1%, but scientists have since recalculated the risk at a reassuring 0.001%.
Tracing the Origins of Asteroids
Most asteroids originate from the asteroid belt between Mars and Jupiter, where they remain under the influence of Jupiter’s gravity. Occasionally, gravitational shifts or collisions with other asteroids send these space rocks into new orbits, some of which bring them dangerously close to Earth.
Studying asteroids provides valuable insights into the formation of the Solar System. Alan Fitzsimmons, an astronomer at Queen’s University Belfast, explains that asteroids are fragments of much larger bodies that existed when the Solar System was forming over 4.6 billion years ago. Analyzing their chemical makeup helps scientists understand the conditions that shaped our planetary neighborhood.
The Science of Asteroid Tracking
Identifying potentially hazardous asteroids is a critical challenge for astronomers. NASA’s Kelly Fast, acting planetary defense officer, explains that asteroids appear as moving points of light in telescopic images. Their brightness helps estimate size, but factors like color and reflectivity can affect accuracy.
NASA and ESA are using the James Webb Space Telescope to observe YR4’s infrared emissions, which may help refine its size estimates and composition. Preliminary data suggest YR4 is a rocky asteroid from the inner asteroid belt, but its exact origins remain unknown.
The Potential for Asteroid Mining
Beyond their risks, asteroids may also hold immense value. Some, like Psyche 16, are believed to contain vast amounts of nickel and iron, similar to Earth’s core. NASA’s Psyche mission, launched to study this metal-rich asteroid, could advance our understanding of planetary formation while also evaluating the feasibility of asteroid mining.
Defending Earth from Future Impacts
The possibility of an asteroid impact has led to increased efforts in planetary defense. NASA’s Double Asteroid Redirection Test (DART) mission, conducted in 2022, successfully altered the orbit of Dimorphos, a small asteroid orbiting a larger one. This test demonstrated that redirecting a hazardous asteroid is possible using kinetic impact technology.
Planetary defense remains a key focus, with international collaborations such as the International Asteroid Warning Network working to detect, monitor, and develop strategies for deflecting future threats.
Looking Ahead
Although YR4 poses no imminent threat, its discovery underscores the importance of tracking and studying asteroids. Scientists remain vigilant, using advanced telescopes and space missions to better understand these celestial bodies. Whether as a potential source of resources or a planetary threat, asteroids continue to shape the past, present, and future of Earth.
