NASA OSIRIX-REx's image of Bennu's 'body armor' unearths new discoveries; details inside

NASA on Friday shared a new photograph beamed back by its OSIRIS-REx spacecraft which was launched to the asteroid Bennu to scoop its samples. The spacecraft, which took off on September 8, 2016, arrived at the asteroid in 2020 and is now on its way to Earth to deliver those samples. According to NASA, the samples will arrive on Earth in 2023 following which, OSIRIS-REx will be redirected to the near-Earth asteroid Apophis under an extended mission.

OSIRIX-REx spacecraft details Bennu’s ‘body armour’

(Image detailing Bennu's surface; credit- NASA)

Short for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer spacecraft, the OSIRIS-REx, in its latest image details the asteroid’s surface which acts as a ‘body armour’. "These observations give new insight into how asteroids like Bennu respond to energetic impacts", said Edward Bierhaus of Lockheed Martin Space, lead author of a paper published in this month’s issue of Nature Geoscience.

According to scientists, Bennu’s boulder-covered surface gives it protection against small meteoroid impacts. Moreover, the space rock is classified as a “rubble-pile” asteroid, meaning it resulted from the debris of a much larger asteroid destroyed during ancient impacts and the fragments coalesced under a weak gravitational pull to form Bennu. The asteroid, which is as big as the Empire state building, around 450 metres wide, was captured in the above image using the spacecraft’s PolyCam camera in April 2019 from a distance of 4.5 kilometres. 

Interestingly, scientists also managed to study its craters and overall topography using a laser-ranging (lidar) instrument on the spacecraft. “Measuring craters and their population on Bennu was exceptionally exciting,” said David Trang of the University of Hawaii and co-author of the paper. “At Bennu, we discovered something unique to small and rocky bodies, which expanded our knowledge of impacts”. 

During their observations, the researchers also found that impact activity on Bennu causes its surface to change differently than objects with fine-grained or solid surfaces. “The displacement or disruption of an individual or small group of boulders by a small impact is probably one of the most fast-acting processes on a rubble-pile asteroid’s surface”, Bierhaus said in a statement. “On Bennu, this contributes to making the surface appear to be many times younger than the interior”. Notably, OSIRIS-REx is NASA’s first mission to collect a sample from an asteroid with the aim to unlock secrets of the universe.