Among the thousands of asteroids that share Earth’s neighborhood, one has been studied more closely than almost any other, and it carries a small but genuine chance of striking the planet in the distant future. The asteroid is Bennu, a dark, rubble-strewn body roughly a third of a mile across, and its most watched moment lies well over a century away, in the year 2182. A NASA spacecraft has already visited it, mapped it and even brought a piece of it home, sharpening what scientists know about where it will go next.
The odds of an actual impact remain very low, and the date is far enough off that no one alive today will see it resolved. But Bennu is a rare case in which humanity has detailed, physical knowledge of an object that could, someday, cross its path, which is exactly why it has become a centerpiece of planetary defense research.
A skyscraper-sized rubble pile
Bennu is a near-Earth asteroid about 500 meters, or roughly 1,640 feet, in diameter, comparable in scale to a tall skyscraper laid on its side. Rather than a solid boulder, it is a loosely bound rubble pile, a heap of rock and dust held together weakly by its own faint gravity. Its dark, carbon-rich surface makes it both a hazard to track and a scientific treasure, because such primitive material preserves chemistry left over from the earliest days of the solar system.
Its orbit brings it periodically close to Earth, which is why it ranks among the potentially hazardous asteroids that agencies monitor continuously. That same accessibility made it an ideal target for a sample-return mission.
Its rubble-pile structure has practical consequences for both science and safety. Because the material is loosely packed, the asteroid is more porous and less dense than solid rock, and its surface proved surprisingly fragile when the visiting spacecraft touched down, spraying debris outward. Understanding how such a weakly bound body would behave matters for any future attempt to deflect it, since a loose pile of rubble responds to a push very differently than a single solid mass.
What OSIRIS-REx learned up close
NASA’s OSIRIS-REx spacecraft rendezvoused with Bennu, orbited it for an extended survey and collected a sample from its surface before sending that material back to Earth. The mission’s precise tracking let scientists at the Jet Propulsion Laboratory calculate the asteroid’s future path with far greater confidence than telescopes alone could provide, pinning down its position through a critical close approach in the year 2135.
Getting that close also revealed how forces beyond simple gravity nudge the asteroid. Sunlight warming and re-radiating from Bennu’s surface produces a tiny but persistent push, and even the sample-collection maneuver itself gave researchers new data on how loosely the surface is bound. Every such detail feeds into predicting where Bennu will be far into the future.
The numbers behind the 2182 encounter
The headline date is September 24, 2182, identified as the single most significant potential impact opportunity, with an estimated probability of about 1 in 2,700. Adding up all the possible impact dates through the year 2300 yields a cumulative chance of roughly 1 in 1,750, according to the University of Arizona, which led the mission’s science team. In plain terms, the overwhelmingly likely outcome is that Bennu misses.
A pivotal wildcard is the 2135 close approach. Earth’s gravity will bend Bennu’s orbit as it passes, and exactly how much depends on precisely where the asteroid threads through the encounter. That flyby will let scientists dramatically refine the odds for the 2180s, replacing today’s estimates with far more certain predictions once it happens.
It is worth putting the 1-in-2,700 figure in perspective. A probability that small means the far likelier outcome, by a wide margin, is a clean miss, and the estimate itself is expected to shrink further as tracking improves rather than to climb toward certainty. Scientists highlight the date not because an impact is expected but because Bennu is one of the few objects whose orbit is known well enough to name a specific date at all. Precision, not danger, is what puts 2182 on the calendar.
Why a distant asteroid is worth the effort
Studying Bennu now, more than a century and a half before any possible impact, buys time and knowledge. If a threatening trajectory were ever confirmed, the many decades of warning would leave ample room to attempt a deflection, and missions like the earlier test that nudged a different asteroid have shown that gently altering an object’s course is technically feasible.
Bennu also serves a purpose beyond planetary defense. The returned sample offers a pristine look at the carbon-rich building blocks of the early solar system, the same kind of material thought to have delivered water and organic compounds to the young Earth. In that sense the asteroid is both a hazard to watch and a time capsule to read, and its 2182 date is less a doomsday countdown than a reason to keep learning everything possible about it.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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