Scientists have calculated the probability that the potentially hazardous Bennu asteroid hits Earth between 2021 and 2300 after studying it for more than two years.
NASA revealed this information in a press release today, saying that while Bennu’s chances of hitting Earth are still very low, the organization has narrowed down its impact probability. It did this by studying its size, shape, mass, composition, spin, and orbital trajectory.
A mosaic of Bennu, Photo Credit: NASA/Goddard/University of Arizona
“Using NASA’s Deep Space Network and state-of-the-art computer models, scientists were able to significantly shrink uncertainties in Bennu’s orbit determining its total impact probability through the year 2300 is about 1 in 1,750 (or 0.057%),” the release reads. “The researchers were also able to identify Sept. 24, 2182, as the most significant single date in terms of a potential impact, with an impact probability of 1 in 2,700 (or about 0.037%).”
OSIRIS-REx spent more than two years in close proximity to Bennu before it finally left the area on May 10 and it studied virtually everything it could about the asteroid. It even grabbed a sample of the asteroid’s rock and dust, which will make its way back to Earth aboard OSIRIS-REX on Sept. 24, 2023.
Study lead Davide Farnocchia said NASA’s never modeled an asteroid’s trajectory to this level of precision — a very high degree of certainty through 2135 — before. The measurements OSIRIS-REx took allow NASA to determine Bennu’s orbit over time and whether or not it will pass through a gravitational keyhole, which is “an area in space that would set Bennu on a path toward a future impact with Earth if the asteroid were to pass through them at certain times due to Earth’s gravitational pull,” during its 2135 approach.
The team also studied the Yarkovsky effect and how it effects Bennu.
“Among those forces, the Sun’s heat plays a crucial role,” the release reads. “As an asteroid travels around the Sun, sunlight heats up its dayside. Because the asteroid spins, the heated surface will rotate away and cool down when it enters the nightside. As it cools, the surface releases infrared energy, which generates a small amount of thrust on the asteroid.”
Study co-investigator Steve Chesley said the Yarkovsky effect affects all asteroids, including Bennu. OSIRIS-REx gave NASA the first opportunity to measure this effect as Bennu traveled around the Sun. Chesley said the effect on Bennu is equivalent to “the weight of three grapes constantly acting on the asteroid.” They also said that effect is tiny but significant in determining Bennu’s future impact over the decades and centuries to come.
Other include the Sun’s gravity, the planets, their moons, and other asteroids in its path. The team also studied the pressure of solar wind, the drag caused by interplanetary dust, and Bennu’s particle-ejection events. They even had to take into account the force OSIRIS-REx exerted on Bennu when it collected the rock sample and left the asteroid’s surface.
“Although a 0.057% impact probability through the year 2300 and an impact probability of 0.037% on Sept. 24, 2182, are low, this study highlights the crucial role that OSIRIS-REx operations played in precisely characterizing Bennu’s obit,” the release reads.
For more about asteroids, read this story about a metallic asteroid between Mars and Jupiter that has an estimated worth of $10,000 quadrillion and then read about how humans could live on a floating asteroid belt in space. Check out this first look at an asteroid sample from space after that, then read about how a meteorite piece found in Africa could be from an ancient planet.
Wesley LeBlanc is a freelance news writer and guide maker for IGN. You can follow him on Twitter @LeBlancWes.