A bus-sized asteroid passed within 56,000 miles of Earth on Monday. That’s roughly a quarter of the distance between Earth and the moon. Scientists confirmed there was no chance of impact, which is the good news. The bad news is that nobody knew it was coming until a few days before.

The asteroid, designated 2026 JH2, measures somewhere between 52 and 115 feet in diameter and was traveling at just over 5 miles per second. Astrophysicist Mark Norris described it to New Scientist as “as close as you can get without hitting,” adding that it’s “the kind of thing that would ruin a city quite efficiently, if it hit.”

Researchers at the Mount Lemmon Survey in Arizona, the Farpoint Observatory in Kansas, and the Magdalena Ridge Observatory in New Mexico spotted it days before its approach. A city-killer with a few days’ notice? That doesn’t seem good. 

A Bus-Size Asteroid Just Flew Past Earth, and Scientists Almost Missed It

The size and speed put JH2 in the same category as the 2013 Chelyabinsk meteor that exploded over Russia. That one was less than 19 miles from Earth when it detonated, released energy roughly 30 times stronger than the Hiroshima bomb, and sent over 1,500 people to the hospital. Nobody saw that one coming either, which is exactly the problem.

JH2 was the ninth-closest known asteroid flyby within one lunar distance recorded this year, and that number probably sounds quite high to many people. According to AstroPhilesz, 73 known asteroids will pass within one lunar distance of Earth in 2026. “This is not a rare event,” the group wrote on Facebook. “Space rocks pass through our neighborhood regularly. Most are discovered with very little warning. That is not enough time to do anything about it if the trajectory had been different.”

Near-Earth objects go undetected until they’re practically on top of us for a simple reason. They’re small, fast, and nearly invisible against the backdrop of deep space. Detection systems have improved, and NASA’s DART mission proved that deflecting an asteroid is actually possible. We can move them. That part is encouraging, at least.

What’s less encouraging is that a rock capable of leveling a city passed Earth on Monday, and the world found out about it sometime last week. If the trajectory had been slightly different, a few days is not a lot of runway.