Scientists have learned something astonishing after analyzing data gathered when sample from asteroid Bennu in October 2020. The spacecraft would have sunk into the asteroid had it not fired its thrusters to back away immediately after it grabbed its sample of dust and rock from Bennu’s surface.
“Our expectations about the asteroid’s surface were completely wrong.” — Dante Lauretta, principal investigator of OSIRIS-REx
Unexpectedly, it turns out that the particles making up Bennu’s exterior are so loosely packed and lightly bound to each other that if a person were to step onto the asteroid they would feel very little resistance. It would be like stepping into a pit of plastic balls that are popular play areas for kids.
“If Bennu was completely packed, that would imply nearly solid rock, but we found a lot of void space in the surface,” said Kevin Walsh, a member of the OSIRIS-REx science team from Southwest Research Institute, which is based in San Antonio.
The latest findings about Bennu’s surface were published on July 7, 2022, in a pair of papers in the journals Science and Science Advances, led respectively by Dante Lauretta, principal investigator of OSIRIS-REx, based at University of Arizona, Tucson, and Kevin Walsh. These surprising results add to the intrigue that has gripped scientists throughout the OSIRIS-REx mission, as Bennu has proved consistently unpredictable.
The first surprise the asteroid presented was in December 2018, when NASA’s spacecraft arrived at Bennu. The OSIRIS-REx team found a rough surface littered with boulders instead of the smooth, sandy beach they had expected based on observations from Earth- and space-based telescopes. Reasearchers also discovered that Bennu was ejecting particles of rock from its surface into space.
“Our expectations about the asteroid’s surface were completely wrong,” said Lauretta.
The latest clue that Bennu was not what it seemed came after the OSIRIS-REx spacecraft picked up a sample and beamed stunning, close-up images of the asteroid’s surface to Earth. “What we saw was a huge wall of debris radiating out from the sample site,” Lauretta said. “We were like, ‘Holy cow!’”
Near-Earth asteroid Bennu is a rubble pile of rocks and boulders left over from the formation of the solar system. On October 20, 2020, NASA’s OSIRIS-REx spacecraft briefly touched down on Bennu and collected a sample for return to Earth. During this event the spacecraft’s arm sank far deeper into the asteroid than expected, confirming that Bennu’s surface…
Read More: Surprise – Again! NASA Spacecraft Reveals Asteroid Bennu Is Not What It Seemed