A City-Killing Asteroid Will Narrowly Miss the Earth Today. We Discovered It Only a Week Ago.

Here’s the good news: If a near-Earth object (NEO) big enough to wipe out humanity entirely is ever on a collision course with our planet, we’re likely to find out about it a good while before it actually happens, maybe allowing us to do something about it before the object arrives. And here’s the counterpoint likely to keep you up at night: For smaller objects, the kind that might only level a single city or wipe out a few million people here or there, it’s entirely likely that we’d find out about it when it’s far too late to do anything. Or find out about it in the moment that some city vanishes in a hellish fireball. You want a demonstration of how little warning we’re likely to have? Well then, turn your gaze upward, because it’s whizzing past the Earth this evening.

Said asteroid, potentially the size of two school buses, is named 2026JH2 and was discovered all of eight days ago, on May 10, by astronomers at the Mount Lemmon Survey in Tucson, Arizona. At around 6 p.m. EST today, 2026JH2 will make an extremely close pass of the Earth, at about 24% of the average distance between the Earth and the moon. It’s a distance equal to only 2.5 times the average distance at which our own geosynchronous satellites tend to orbit the planet for purposes like telecommunications. That, cosmically speaking, is very close indeed, at roughly 56,913 miles.

In terms of size, 2026JH2–which originated in the Asteroid Belt of our own solar system–is estimated to be about 50 to 100 feet in diameter. That’s plenty big enough to do some very serious damage, although this depends almost entirely on where and how that kind of object strikes the Earth. On the low end of the size estimate, we might be talking about an asteroid similar in impact to the Chelyabinsk meteor, which exploded in an early morning airburst over Russia’s Chelyabinsk Oblast on Feb. 15, 2013, captured on numerous dash cams and security footage. This incident demonstrated what a relatively small NEO impact (in this case an airburst) could look like over a populated area: More than 1,400 people were injured seriously enough to seek medical treatment, mostly because of glass from ruptured windows that were blown in by the resulting shockwave. More than 7,000 buildings across six cities sustained degrees of damage from the blast, estimated to have been in the range of a half megaton of TNT. Dropped directly on any of those cities, the results could have been comparable to that of conventional nuclear weapons.

On the larger side of the potential size estimates for asteroid 2026JH2, meanwhile, we have the possibility of recreating an event such as the legendary Tunguska blast of 1908, in which another large meteor or asteroid is speculated to have exploded in the sky over East Siberia–thankfully far from population centers. Nevertheless this explosion, the largest measured from an impact event in human history, likely produced a blast with a destructive power of 5 to 10 megatons of TNT, equal to some of the most devastating hydrogen bombs ever assembled and tested by humanity at the height of the cold war. The accompanying shockwave broke windows and knocked people off their feet hundreds of kilometers from the actual site of the airburst.

So yeah, something on that level is passing by the Earth today, at a range equal to 24% that of our own moon. And we learned that this potential threat existed eight days ago.

It likely goes without saying that even if we calculated a week ago that such a rock was actually going to collide with Earth, we would be mostly powerless to stop it. Neither the USA nor our allies have interceptor rockets waiting on launchpads, ready to go to intercept and collide with such a near-Earth object. And even if we did, it might be entirely pointless to go through with such a mission, because the object in question would already be far too close in order for us to measurably alter its course in the last few days before it strikes the Earth. NASA’s impressive Double Asteroid Redirection Test (DART) was launched in 2021 to test this hypothesis, colliding with the asteroid Dimorphos in 2022 to study how much we could change its flight path. The results were encouraging, but such a tactic is one that humanity would need to employ against a space rock that is going to strike the Earth not in days or months, but years, in order to take advantage of the microscopic changes in its flight path that we can achieve through actions such as slamming a satellite/spacecraft into it. With an object that will be making impact with Earth in days or months, we’d mostly be left to simply prepare for the worst.

The relatively good news, there, is that even with roughly 8.3 billion people on Earth, our actual surface area is mostly not urban centers: Cities account for roughly 1-3% of the planet’s land surface, and 70% of the entire surface is covered by water. An asteroid like 2026JH2 could thus accurately be called a “city killer” in potential, but the odds that it would actually strike physically near a city or urban center is still low. We might even be able to predict with relative precision where such an impact would occur, and warn local residents to take shelter … not that we were able to do so in a case like the Chelyabinsk meteor, which was entirely undetected. In fact, oddly enough, astronomers were already paying close attention that same day to the near Earth approach of another asteroid, 367943 Duende, only to find that the Chelyabinsk meteor had entirely snuck up on them.

Tomorrow, asteroid 2026 JH2 will pass less than 1/4 the distance of the Moon as it flies over South Africa. #astro 🔭

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— Tony Dunn (@tony873004.bsky.social) 6:13 PM · May 17, 2026

Reading that, one can’t help but think about the anticipated arrival of another NEO, the much larger (nearly 1,500 feet) 99942 Apophis, which is expected to pass even closer to Earth at a range of just 19,883 miles on April 13, 2029, and wonder what unknown stones still linger in its wake. The close passage of Apophis, once feared as representing a very real but slim chance of an extinction-level event, will no doubt be heavily observed as a chance for scientific study, but all my mind can return to is the roulette spin represented by smaller asteroids such as the totally unheralded 2026JH2. How many years or decades will it be before our technology can reliably spot and categorize all of those potential city killers? There are more than 1.5 million asteroids catalogued in the NASA Jet Propulsion Laboratory’s database, but astronomers have apparently observed only about 1% of all the near-Earth asteroids with a similar makeup to 2026JH2. According to Professor Jean-Luc Margot of the University of California, speaking to CNN: “It’s not surprising that this object was discovered only a few days before its closest approach to Earth, when it became bright enough to be picked up by asteroid detection surveys.”

It’s a reminder that ultimately, our planet is always threading its way through space on a wing and a prayer, relying upon probability to spare us from the kind of intersection of bodies that once flattened a forest in Tunguska in 1908, or wiped out the dinosaurs entirely 65 million years ago. Tonight, 2026JH2 may whiz right past us at a distance of one-quarter moon length, but a day is eventually coming when such a rock will not be dissuading from paying our planet a visit. Here’s hoping we’re finally ready when it does, but I wouldn’t count on it.