Over 15,000 “City-Killer” Asteroids Are Out There — And We Haven’t Found Them Yet

NASA has identified around 25,000 asteroids large enough to destroy an entire city if they hit Earth. The alarming part? We’ve only tracked about 40% of them — meaning more than 15,000 are still out there, undetected.

To understand just how serious this is, look back at 1908. An asteroid estimated to be around 160–200 feet wide exploded over Siberia, Russia, and wiped out over 800 square miles of forest. If that had happened over a city, the destruction would have been unimaginable.

So why can’t we find these asteroids?

Many of them are very dark, meaning they don’t reflect sunlight well and are hard to spot with regular telescopes. Others hide in the glare of the Sun, where our ground-based telescopes can’t easily look.

The biggest challenge is time. We can actually deflect asteroids — NASA proved this in 2022 when its DART spacecraft successfully changed the orbit of an asteroid. But to do that, we need to find a dangerous asteroid years in advance.

That’s where the Near-Earth Object Surveyor comes in. NASA is building this infrared space telescope specifically to detect dark, hard-to-spot asteroids using heat instead of light. It’s expected to launch between 2027 and 2028, with the goal of tracking 90% of near-Earth threats within a decade.

The bottom line: we have the technology to protect our planet — but first, we need to find what’s coming.