An asteroid considered one of the most hazardous objects hurtling through space remains highly unlikely to strike Earth in the next three centuries, although the chances have increased slightly, according to data collected by an asteroid-exploring spacecraft and released Wednesday by NASA and Jet Propulsion Laboratory in Pasadena.
The asteroid known as Bennu, with a diameter rivaling the Empire State Building, won’t make another close pass by Earth until 2135.
According to a trajectory-analysis based on data collected by NASA’s OSIRIS-REx mission — Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer — the odds of the asteroid striking Earth through the year 2300 are roughly 1 in 1,750, or 0.057%. NASA had previously estimated the odds of an impact occurring between 2175 and 2199 at about 1 in 2,700.
NASA officials said Wednesday they still have no immediate concerns about a potential impact, noting the “probability remains small.”
Researchers said data collected by OSIRIS-REx provided confidence that the asteroid will pose little threat to the Earth before or during the 2135 pass.
“The OSIRIS-REx data give us so much more precise information, we can test the limits of our models and calculate the future trajectory of Bennu to a very high degree of certainty through 2135,” according to study lead Davide Farnocchia of the Center for Near-Earth Object Studies at JPL. “We’ve never modeled an asteroid’s trajectory to this precision before.”
OSIRIS-REx spent more than two years in close proximity to the asteroid, and even collected samples from its surface. Those samples will be returned to Earth in September 2023 for further analysis. In particular, the mission helped researchers understand the potential effects of a phenomenon known as the Yarkovsky effect on the asteroid’s future trajectory.
The effect is the result of the sun’s heat warming part of the asteroid’s surface. As the asteroid spins, turning the heated surface away from the sun, the resulting cooling can generate a small amount of thrust. Although the effect is considered “miniscule,” over a long period of time it can affect the asteroid’s ultimate trajectory.
“The Yarkovsky effect will act on all asteroids of all sizes, and while it has been measured for a small fraction of the asteroid population from afar, OSIRIS-REx gave us the first opportunity to measure it in detail as Bennu traveled around the sun,” said Steve Chesley, senior research scientist at JPL and study co-investigator. “The effect on Bennu is equivalent to the weight of three grapes constantly acting on the asteroid — tiny, yes, but significant when determining Bennu’s future impact chances over the decades and centuries to come.”
As a result, researchers will be keeping an eye on the asteroid for centuries to come. Projections currently show the asteroid’s highest odds of an impact with Earth in 2182, but even then, the chance is only 0.037%.
“The orbital data from this mission helped us better appreciate Bennu’s impact chances over the next couple of centuries and our overall understanding of potentially hazardous asteroids — an incredible result,” said Dante Lauretta, OSIRIS-REx principal investigator and professor at the University of Arizona. “The spacecraft is now returning home, carrying a precious sample from this fascinating ancient object that will help us better understand not only the history of the solar system but also the role of sunlight in altering Bennu’s orbit since we will measure the asteroid’s thermal properties at unprecedented scales in laboratories on Earth.”