Hazardous Asteroid Bennu To Make Close Approach To Earth: NASA's OSIRIS-REx Mission Reveals Key Insights

Bennu is unlikely to pose a danger during the 2135 encounter, scientists are studying data from OSIRIS-REx spacecraft to understand the asteroid’s exact trajectory and future orbits.

This mosaic of Bennu was created using observations made by NASA’s OSIRIS-REx spacecraft that was in close proximity to the asteroid for over two years. (Credits: NASA/Goddard/University of Arizona)

New Delhi: Bennu, a known potentially hazardous asteroid, will make a close approach to Earth in 2135, NASA has said after studying the findings from its Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft that spent two years in close proximity to the near-Earth object.

OSIRIS-REx is on its way back to Earth with rock and dust samples from Bennu. While the samples will reach only in September 2023, information and data collected by the spacecraft have already given scientists a greater understanding of Bennu, its future approaches to our planet, and the chances of them impacting the Earth.

Though Bennu is unlikely to pose a danger during the 2135 encounter, understanding the asteroid’s exact trajectory could help scientists better understand how the gravity of Earth will change Bennu’s future orbits around the sun, the space agency said.

The researchers were able to identify September 24, 2182, as the next most significant single date for a potential impact, with a 1 in 2,700 (about 0.037%) probability of Bennu impacting Earth on that day.

Bennu is one of the two most hazardous known asteroids, along with 1950 DA, in our solar system. 

NASA shared the findings on Wednesday. The study, titled “Ephemeris and hazard assessment for near-Earth asteroid (101955) Bennu based on OSIRIS-REx data”, was released Wednesday and published in the journal, Icarus.

“NASA’s Planetary Defense mission is to find and monitor asteroids and comets that can come near Earth and may pose a hazard to our planet,” said Kelly Fast, manager of Near-Earth Object Observations Program, at NASA Headquarters in Washington. 

“We carry out this endeavor through continuing astronomical surveys that collect data to discover previously unknown objects and refine our orbital models for them. The OSIRIS-REx mission has provided an extraordinary opportunity to refine and test these models, helping us better predict where Bennu will be when it makes its close approach to Earth more than a century from now.”

Using the precision-tracking data from OSIRIS-REx to understand the asteroid's movements through the year 2300, the scientists were able to reduce the uncertainties they had about Bennu’s future orbit — it has a 1 in 1,750 chance of impacting Earth in 2300.

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OSIRIS-REx Visit To Bennu

The OSIRIS-REx mission was launched on September 8, 2016, from NASA’s Cape Canaveral Air Force Station, and it reached asteroid Bennu in December 2018.

The spacecraft spent over two years in close proximity to the asteroid, during which it gathered information about its size (about 500 m wide), shape, mass, and composition, and also monitored its spin and orbital trajectory. 

Before leaving the asteroid on May 10, 2021, the spacecraft collected the sample of rock and dust from Bennu’s surface, which it will return to Earth on September 24, 2023, for further scientific studies.

“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,” said study lead Davide Farnocchia, from the Center for Near-Earth Object Studies, managed by NASA’s Jet Propulsion Laboratory in Southern California. “We’ve never modeled an asteroid’s trajectory to this precision before.”

NASA said though the 0.057 percent impact probability through 2300 and the 0.037 percent chance of an impact on September 24, 2182, are low, the study brings to the fore the crucial role the OSIRIS-REx operations played in characterising Bennu’s orbit with precision.

With the spacecraft now on its way back, the rock and dust samples it is bringing will help scientists “better understand not only the history of the solar system but also the role of sunlight in altering Bennu’s orbit”, said Dante Lauretta, OSIRIS-REx principal investigator, and professor at the University of Arizona.

He said they would now measure Bennu’s thermal properties at “unprecedented scales”.