NASA refines threat posed by potentially dangerous asteroid Bennu

Data collected over the years NASA’s OSIRIS-REx bypassed the asteroid Bennu has enabled scientists to uncover the risk posed by this potentially dangerous near-Earth object.

The OSIRIS-REx spacecraft is currently en route to Earth, carrying surface samples it collected from the asteroid Bennu. From December 2018 to May 2021, the NASA spacecraft studied the gigantic pile of rubble from all angles, measuring its size, shape, mass, composition, rotation, orbital path and other important characteristics. Bennu is a primitive carbonaceous asteroid, so by studying this object scientists can make inferences about what our solar system looked like during its formative period.

But this $ 800 million mission is not limited to the simple search for organic molecules or signs of water and heavy elements. Bennu is currently ranked second on the listing potentially dangerous asteroids, stressing the importance of learning as much as possible about it, especially the orbital dynamics that dictate its future movements.

New research, published in Icarus, does just that, providing a refined trajectory of Bennu up to the year 2300. The misanthropists among you may be happy to learn that Bennu still has a very slim chance of hitting our planet in the next century. . The probabilities of a collision in the year 2300, however, remain very low: they are now estimated at around 1 in 1750, or 0.057%.

Data derived from OSIRIS-REx, NASA’s Deep Space Network and computer models allowed scientists to limit uncertainties in Bennu’s orbit by a factor of 20. OSIRIS-REx is what really made this possible. , because he measured Bennu’s position relative to the Earth down to the scale of a few meters.

Speaking earlier today on a conference call for reporters, Davide Farnocchia, lead author of the new article and researcher at the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory in Southern California, said stated that this was an “impressive” result, like “we had one of the best-known orbits in the entire asteroid catalog,” in reference to Bennu. Dante Lauretta, co-author of the OSIRIS-REx study and principal investigator at the University of Arizona, said this “incredible accuracy” has allowed the team to characterize the asteroid’s orbital parameters and better predict where it will be in the future.

Impressively, the new model allowed researchers to eliminate 24 of 26 possible keyholes for Bennu that were to exist on September 11, 2135, when the asteroid was expected to pass safely past Earth. Gravitational keyholes can be compared to fictional gateways that take characters to alternate timelines (fans of the new Loki series know what I’m talking about). Keyholes are very real, however, and that’s bad news – we don’t want asteroids to pass through keyholes, as they are gateways that take asteroids on orbital paths that threaten Earth.

There is no chance of an impact at that meeting in 2135, Farnocchia said, but Bennu will be close to Earth – about half the distance from Earth to the Moon – and that will change the trajectory of the Earth. asteroid. To know this change in trajectory, however, scientists have to consider gravitational keyholes.

Like NASA describe them, keyholes are “areas in space that would put Bennu on the path to future impact with Earth if the asteroid were to pass through them at certain times, due to the effect of gravitational pull. of the earth”. The new research describes two keyholes still in play, one of which would involve a collision between Earth and Bennu on September 24, 2182 (note your calendars), but the probability is slim, at 1 in 2,700, or 0.037%. As Farnocchia repeatedly reminded reporters at the press conference, “there is no reason to worry”.

The reason for so much uncertainty has to do with all the variables involved. Sir Isaac Newton described a universe that operates with clock-like precision, but the clock that is our solar system has an unspeakable number. moving parts. These disruptive influences include things like the Sun’s gravity, the planets, all moons, hundreds of asteroids, interplanetary dust, and the solar wind.

For the new study, Farnocchia and his colleagues tried to factor in as many variables as possible to predict Bennu’s future trajectory, including the masses of 343 known asteroids. They even reported on a possible nudge exerted by OSIRIS-REx when grasped a sample of surface material on October 20, 2020 (it was found to be negligible) and pieces of debris which naturally fall from Bennu (also not a factor).

There is also the Yarkovsky effect to consider. This is what happens when an object absorbs radiation from the Sun and this radiation then escapes. This changes the momentum of an object in space, causing it to drift slightly from the path otherwise dictated by gravity. This effect is very small, but it becomes significant over large time scales. OSIRIS-REx gathered invaluable information – information that was difficult, if not impossible to collect from the ground – that was used to calculate the Yarkovsky effect as Bennu traveled around the Sun, including size, mass, shape, the object’s rotation, surface properties and more. factors, as Farnocchia explained. It “helped us model Bennu’s future movement,” he added.

Interestingly, the samples collected by OSIRIS-REx could deepen our understanding of how the Yarkovsky eThe effect could continue to change Bennu’s trajectory. Analysis of surface samples could “expose changes to the asteroid over time, such as weathering of the surface,” which “would improve our understanding of one of the most important parameters in determining orbital trajectory. As Lauretta explained in response to a question from yours. really.

The new research provides the strongest estimates of Bennu’s future to date, but there is still room for improvement. The researchers would like to explain the gravitational influence of all the asteroids in the solar system; determining the mass of these asteroids would be “a major next step,” Farnocchia said. Bennu’s improved mass and density measurements, which are still uncertain, would also be useful. Bennu is a loose pile of rocks and dust that likely has empty cavities and an uneven distribution of material below the surface.

And now we are waiting September 24, 2023, when OSIRIX-REx is defined to come back to Earth with his samples. Lauretta said the mission was “in great shape right now,” which is obviously good news. There is still a lot to learn about this fascinating and perhaps disturbing – asteroid.