No need to duck and cover. Asteroid 2024 RW1 is only a few feet in diameter. That’s not big enough to cause problems as it smashes into Earth’s atmosphere. What’s cool about 2024 RW1 is that it was discovered only hours before its expected impact over the Western Pacific near the Philippines on Sept. 4. “Discovered this morning by the Catalina Sky Survey, this is just the ninth asteroid that humankind has ever spotted before impact,” the European Space Agency said on social media.

The discovery of the small asteroid is a sign that Earth’s planetary defense programs are working as intended. Planetary defense isn’t about preparing for alien invasions. It’s about finding, tracking and understanding space rocks that might impact our atmosphere and cause damage down below. Earth has a history of asteroid and comet strikes, which can leave craters or burst in the air. Space agencies like NASA and ESA are keeping tabs on known potentially hazardous space objects and are always looking for new ones to track.

The Catalina Sky Survey is a NASA-funded project based out of the University of Arizona. CSS uses telescopes and advanced software to find potentially hazardous asteroids. It has a history of spotting small space rocks hours before impact and then rapidly calculating trajectory and impact timing. That’s enough time to give people in the path a heads-up. CSS shared images of 2024 RW1 on X. It appears as a faint smudge circled in purple.

Even a small asteroid like 2024 RW1 can create a huge, spectacular fireball visible to observers on the ground. ESA fielded questions about the space object on X. “An object this size has the potential to create a stunning fireball, but weather conditions in the area are likely to be cloudy and stormy,” the space agency said. A tropical storm in the region was likely to obscure fireball viewing.

A commenter asked if the last-minute discovery was concerning. “This detection is actually great news!” ESA replied, calling it “a sign of our improving planetary defense capabilities.” CSS discovered an asteroid in January before impact. That asteroid delivered sonic booms and a bright flash of light over the Toronto, Ontario region of Canada. Some reports noted ground shaking. The space rock was roughly the size of 2024 RW1. Even small asteroids like those can send small pieces all the way to the Earth’s surface. If 2024 RW1 drops debris, it will likely land in the ocean.

NASA and ESA don’t expect any truly Earth-threatening space rocks for quite some time. “There is currently no known significant threat of impact for the next hundred years or more,” NASA said in an Asteroid Watch explainer. The agency has cataloged over 35,000 near-Earth objects (mostly asteroids) and the number continues to rise—thanks in part to our improved ability to spot small space rocks like 2024 RW1. The dainty asteroid visitor will meet a fiery demise, but it will have made a valuable contribution to the science of planetary defense.