We've never modeled an asteroid's trajectory with this precision
Across more than two years of close observation, a NASA spacecraft has given humanity its most precise reckoning yet with a question as old as our awareness of the cosmos: what are the odds that a rock from space will one day find us? The asteroid Bennu, a rubble-pile world half a kilometer wide, carries a 1-in-2,700 chance of striking Earth on September 24, 2182—a probability refined by the OSIRIS-REx mission from a cloud of uncertainty into something science can now hold with confidence. The news is not that danger has been erased, but that it has been measured, and in measurement there is a particular kind of human reassurance.
- Bennu was already considered one of the most hazardous known asteroids, and before OSIRIS-REx, scientists feared it might pass through as many as 26 gravitational keyholes—narrow corridors in space where Earth's gravity could redirect it onto a collision course.
- New spacecraft data has collapsed that list of dangerous keyholes from 26 down to just 2, dramatically sharpening the picture of what the next three centuries may hold.
- The critical moment arrives in 2135, when Bennu will pass close enough for Earth's gravity to bend its orbit around the Sun—making that non-threatening flyby the hinge on which all future impact calculations turn.
- Tiny but relentless forces—solar heat pushing like the weight of three grapes, ejected surface particles, gravitational tugs from planets and moons—mean scientists must keep watching, because the math is never truly finished.
- NASA's planetary defense teams are treating OSIRIS-REx not just as a sample-return mission but as a live stress-test of the orbital models humanity would rely on if a genuine threat ever needed to be confronted.
A spacecraft that spent more than two years orbiting asteroid Bennu has delivered the clearest forecast yet of where that ancient rock is headed. The verdict is cautiously reassuring: Bennu carries a 1-in-2,700 chance of striking Earth on September 24, 2182, and a 99.94 percent probability of missing us entirely through the year 2300. These are not guesses—they are the product of trajectory modeling made possible by NASA's OSIRIS-REx mission, which arrived at Bennu in late 2018 and departed in May 2021 carrying a surface sample bound for Earth in 2023.
Before this study, scientists had identified as many as 26 gravitational keyholes—small pockets of space where Earth's pull during a future flyby could redirect Bennu onto a dangerous path. OSIRIS-REx data reduced that number to just two. Lead researcher Davide Farnocchia noted that the mission allowed the team to model Bennu's trajectory with a precision never before achieved for any asteroid.
The physics involved is humbling in its detail. Bennu, roughly 500 meters wide and shaped like a spinning top, is not a solid rock but a gravity-bound rubble pile. Its closest approach in 2135 will not threaten Earth, but that passage is pivotal—Earth's gravity will subtly reshape Bennu's solar orbit, and understanding that deflection is essential to predicting what comes after. Meanwhile, the Sun's heat creates a continuous tiny push known as the Yarkovsky effect, described by one NASA scientist as equivalent to the weight of three grapes pressing constantly against the asteroid. Over centuries, that pressure adds up.
Kelly Fast of NASA's Planetary Defense program described OSIRIS-REx as an extraordinary opportunity to test and refine the models her agency depends on. Principal investigator Dante Lauretta echoed that view, calling the orbital data a remarkable bonus alongside the mission's primary goal of returning a physical sample. The risk from Bennu remains low—but the work of measuring it, force by tiny force, century by century, goes on.
A spacecraft that spent more than two years circling an asteroid has given scientists their clearest picture yet of where that rock is headed—and the news is reassuring, if not entirely risk-free. The asteroid Bennu, one of the solar system's most hazardous known objects, will pass closest to Earth on September 24, 2182. On that day, it carries a 1-in-2,700 chance of impact. Over the full span through the year 2300, the odds compress further: just 1 in 1,750. Put another way, there is a 99.94 percent probability that Bennu will not hit us at all.
These numbers come from data collected by NASA's OSIRIS-REx mission, which arrived at Bennu in December 2018 and departed in May 2021 carrying a sample from the asteroid's surface. That sample will reach Earth in September 2023. But the spacecraft has already been transmitting findings that have transformed how scientists understand Bennu's movements and future path. The mission allowed researchers to track the asteroid's trajectory with unprecedented precision all the way to 2300—a refinement that has dramatically reduced the uncertainties that once clouded their models.
Before this study, scientists worried that Bennu might pass through as many as 26 gravitational keyholes—small regions of space where Earth's gravity could alter the asteroid's orbit and potentially set it on a collision course with our planet. New data has narrowed that list to just two. Davide Farnocchia, the lead author of the study published in the journal Icarus, explained that the OSIRIS-REx information allowed them to test the limits of their models and calculate Bennu's future path with a degree of certainty never before achieved. "We've never modeled an asteroid's trajectory with this precision," he said.
Bennu itself is roughly 500 meters wide, shaped like a spinning top, and held together by gravity—a rubble pile of rocks rather than a solid body. During its closest approach in 2135, it will not threaten Earth, but that passage matters enormously. Earth's gravity will tug at Bennu and alter its orbit around the Sun. Understanding exactly how that deflection will work is the key to predicting whether the asteroid might later be nudged into a dangerous path. The OSIRIS-REx data made that calculation possible.
Several forces continuously reshape Bennu's orbit. The Sun's heat causes what scientists call the Yarkovsky effect: as the asteroid spins through cycles of warming and cooling, it releases energy and receives a tiny push. Steve Chesley, a senior research scientist at NASA's Jet Propulsion Laboratory, described the effect as equivalent to the weight of three grapes pushing constantly on the asteroid. Minuscule, yes—but significant enough to matter across decades and centuries. Gravity from the Sun, other planets, moons, and asteroids all play a role. So do solar wind and dust. During the mission, the team was surprised to observe Bennu's surface ejecting particles into space, another force that could influence its path.
Kelly Fast, manager of NASA's Planetary Defense program, emphasized that the agency's mission is to find and monitor asteroids and comets that might approach Earth and pose a danger. "We conduct this effort through ongoing astronomical surveys that collect data to discover previously unknown objects and refine our orbital models for them," she said. "OSIRIS-REx has provided an extraordinary opportunity to refine and test these models, helping us predict with much greater confidence where Bennu will be when it approaches Earth more than a century from now."
Dante Lauretta, the principal investigator for OSIRIS-REx and a professor at the University of Arizona, called the orbital data a remarkable result. While the mission's primary goal was to collect and return a sample from Bennu, the information gained about near-Earth objects and the ability to calculate their orbits with far greater accuracy has proven invaluable. NASA will continue watching Bennu's orbit in the years ahead. The risk remains low, but the work of understanding it—of measuring forces as small as the weight of grapes and tracking a rock across centuries—continues.
Notable Quotes
The OSIRIS-REx data allows us to test the limits of our models and calculate Bennu's trajectory with high certainty until 2135, achieving a level of precision never before accomplished in asteroid modeling.— Davide Farnocchia, lead author of the study, NASA's Center for Near Earth Object Studies
The Yarkovsky effect on Bennu is equivalent to the weight of three grapes acting constantly on the asteroid—tiny, but significant for determining Bennu's impact chances in the decades and centuries ahead.— Steve Chesley, senior research scientist, NASA Jet Propulsion Laboratory
The Hearth Conversation Another angle on the story
Why does it matter that we've narrowed the gravitational keyholes from 26 down to 2? Doesn't that still leave room for impact?
It matters because each keyhole represented a window of uncertainty. Before, we couldn't rule out 26 different ways Earth's gravity might redirect Bennu toward us. Now we can say with confidence that only 2 scenarios remain possible. The odds have shifted from "we don't know" to "we're pretty sure it's fine."
But the Yarkovsky effect—three grapes worth of force—sounds impossibly small. How does that change anything?
Over a century or more, tiny forces compound. Imagine pushing a shopping cart with the weight of three grapes. One push seems nothing. But push it every day for a hundred years, always in the same direction, and you've moved it miles. That's what happens to Bennu.
The spacecraft is still two years away from returning the sample. Why are we getting these results now?
Because OSIRIS-REx has been transmitting data the whole time it orbited Bennu. Scientists didn't wait for the sample to land—they've been analyzing what the spacecraft learned about the asteroid's shape, composition, and behavior. The sample will add more detail, but the trajectory work is already done.
If the chance of impact is 1 in 2,700 in 2182, should people be worried?
Not in any practical sense. That's a 99.96 percent chance of safety. But the real value isn't reassurance—it's that we now know this with precision. A century and a half from now, if Bennu's path does shift, we'll have the data to understand why and potentially do something about it.
What could we actually do if Bennu were on a collision course?
That's beyond this story, but the foundation is what OSIRIS-REx has given us: accurate knowledge of where the asteroid is and how it moves. You can't deflect something you don't understand.