Artist rendering of Nasa's OSIRIS-REx spacecraft

Bennu asteroid poses greater threat to Earth than previously thought, Nasa says

Image credit: reuters

The Bennu asteroid is more likely to hit the Earth next century than previously thought, Nasa has said, although the chance is still slim.

Researchers from the space agency used precision-tracking data from the OSIRIS-REx spacecraft (pictured above) to better understand the potentially hazardous asteroid’s movements.

OSIRIS-REx was launched in 2016 with the primary mission of studying Bennu and ultimately returning a sample of it back to Earth for detailed analysis. It is believed to have successfully collected that sample last October and is currently undergoing the two-year trip back home.

With a firmer understanding of its path, Nasa scientists now believe the odds of Bennu striking the Earth have risen from 1 in 2,700 to 1 in 1,750 over the next century or two.

In 2135, it will make a close approach with Earth, although it will not pose a danger at that time. Nasa said scientists will need to get a grip on its exact trajectory during the encounter in order to predict how Earth’s gravity will alter the asteroid’s path around the Sun and affect the chances of an Earth impact.

“Nasa’s Planetary Defence 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 at Nasa’s Near-Earth Object Observations Program.

“We carry out this endeavour 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.”

The researchers believe that 24 September 2182 is the most significant single date in terms of a potential impact and although the chances of it hitting Earth are very low, it remains one of the two most hazardous known asteroids in our solar system, along with another asteroid called 1950 DA.

The precision measurements on Bennu help to better determine how the asteroid’s orbit will evolve over time and whether it will pass through a “gravitational keyhole” during its 2135 close approach.

These keyholes are areas 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 the effect of Earth’s gravitational pull.

“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.”

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