An asteroid the size of the Empire State Building has a small shot at Earth in 2182

Asteroid 101955 Bennu is roughly 500 meters across, close to the height of the Empire State Building measured from base to spire, and it spends part of its orbit crossing paths with Earth. NASA scientists have calculated that Bennu carries a small but real chance of striking the planet more than a century and a half from now, a risk precise enough that researchers have pinned down both the total odds through the year 2300 and the single most dangerous date on the calendar. First spotted in 1999, the carbon-rich, rubble-pile asteroid is classified as a potentially hazardous object because of both its size and how closely its orbit periodically brings it to Earth.

A Sample-Return Mission Became a Risk Assessment

The impact math came from an unlikely source: a sample-collection mission. NASA’s OSIRIS-REx spacecraft spent more than two years in close proximity to Bennu, mapping its shape, mass, composition and spin before scooping a sample of rock and dust from its surface in October 2020 and eventually returning it to Earth. That extended close study gave researchers at the Center for Near-Earth Object Studies, managed by NASA’s Jet Propulsion Laboratory, tracking data precise enough to model Bennu’s orbit through the year 2300 with far less uncertainty than typical asteroid predictions allow.

The Numbers Behind the Risk

Using that data, JPL researchers determined Bennu’s total impact probability through 2300 at about 1 in 1,750, or roughly 0.057 percent. They also identified September 24, 2182, as the single riskiest date, carrying an impact probability of about 1 in 2,700, or approximately 0.037 percent. Those figures make Bennu one of two asteroids ranked among the most hazardous known objects in the solar system, alongside a separate asteroid called 1950 DA. Study lead Davide Farnocchia, of JPL’s Center for Near-Earth Object Studies, said the mission produced a level of trajectory modeling precision never achieved for an asteroid before.

Why 2135 Matters More Than 2182

The 2182 date depends heavily on what happens decades earlier. In 2135, Bennu will pass close to Earth, and the exact geometry of that flyby determines whether the asteroid’s subsequent path threads through what scientists call a gravitational keyhole, a narrow region of space where Earth’s gravity could bend the asteroid onto a future collision course. Passing through one of these keyholes at a particular moment would set up a later impact; missing it removes the risk for that date entirely. Researchers cannot yet say with certainty which outcome will occur, which is why the 2182 probability remains a statistical estimate rather than a settled forecast.

A Tiny Push From Sunlight, Compounded Over Decades

Much of the uncertainty in predicting Bennu’s path comes down to a subtle physical effect rather than gravity alone. As the asteroid rotates, sunlight heats its day side, and the heat radiates back into space as the surface cools on the night side, generating a faint thrust known as the Yarkovsky effect. JPL scientist Steve Chesley compared the force acting on Bennu to “the weight of three grapes constantly acting on the asteroid,” negligible on any single day but capable of shifting the asteroid’s position meaningfully over centuries. Modeling that effect accurately, along with the gravitational pull of the sun, planets, moons and more than 300 other asteroids, was central to narrowing the impact-probability estimates.

What a Direct Hit Would Actually Mean

Even in the unlikely event Bennu did strike Earth, researchers have stressed the object falls into the “city-killer” size range rather than the mass-extinction category associated with the asteroid tied to the dinosaurs. A body of Bennu’s size hitting a populated area could level a metropolitan region and cause damage across a wider radius, but it would not threaten civilization globally. NASA’s planetary defense program treats objects like Bennu as priorities for continued tracking precisely because their orbits are well enough understood to calculate specific dates and odds, rather than lumping them into a broader category of unknown risk.

Tracking Continues Long After the Spacecraft Left

OSIRIS-REx departed Bennu in May 2021 and delivered its surface sample to Earth on September 24, 2023, when a capsule parachuted into the Utah desert for recovery. Laboratory analysis of that material has since turned up amino acids and other organic compounds, the raw chemical building blocks associated with life, reinforcing the idea that asteroids like Bennu may have helped seed early Earth with similar ingredients billions of years ago. The orbital study the mission enabled continues to shape how NASA monitors the asteroid today. Ground-based telescopes and the Deep Space Network still refine Bennu’s trajectory as new observations accumulate, and any future data that further narrows the odds around the 2135 keyhole passage would directly update the 2182 probability. For now, the figures stand as one of the most precisely calculated long-range asteroid risk assessments NASA has ever produced.

This article was produced with the assistance of AI and reviewed by an editor.

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