Washington (AFP)

Asteroid Bennu will pass very close to Earth in 2135, just half the distance from our planet to the Moon, NASA said on Wednesday, revealing new data that the chances of a later impact will be here 2300, remain tiny.

Bennu, discovered in 1999 and measuring 500 meters in diameter, is one of the two known asteroids in our solar system posing the most risk to Earth, according to the US Space Agency.

NASA's Osiris-Rex probe spent two years in orbit around Bennu, which it left last May to bring back samples collected during a contact of a few seconds with the ground, and which will arrive on Earth in 2023.

The mission made it possible to study the asteroid very closely, and to considerably improve the predictions on its future trajectory.

By 2300, the chance of a collision with Earth is only 0.057%, the scientists concluded.

"In other words, it means that there is a 99.94% chance that Bennu is NOT on an impact trajectory," said Davide Farnocchia, scientist at NASA's Near Earth Object Studies, during a press conference.

"So there is no need to worry too much."

Why are we not 100% sure?

In September 2135, Bennu will pass very close to Earth.

This will give it the possibility of crossing what is called a "gravitational keyhole": an area which would slightly alter the trajectory of the asteroid, because of the gravitational influence of our planet, thus putting it on a trajectory of future collision.

Before the Osiris-Rex mission, 26 "keyholes" a kilometer or more large were possibly in Bennu's path in 2135.

Thanks to the analyzes allowed by the Osiris-Rex probe, scientists were able to exclude 24. The last two remain.

The most likely date of impact would then be in 2182, according to them.

If it happened, the event would be catastrophic.

“Typically, the size of a crater will be 10 to 20 times the size of the object,” said Lindley Johnson of NASA's Planetary Defense Coordination Office.

Or for Bennu, a crater between 5 and 10 km in diameter.

“But the destruction zone will be much larger than that, up to 100 times the size of the crater,” he said.

He said the researchers knew about 79% of asteroids the size of Bennu and close to Earth.

And Davide Farnocchia recalled: "The risk posed by Bennu is actually smaller than the risk posed by objects of similar size that we have not yet discovered".

© 2021 AFP