All the Rocks
Three research papers on Bennu have recently been published as scientists analyze all the data collected by the OSIRIS-REx mission in space.
Research papers on Bennu have been coming out in droves these days as scientists analyze all the data collected by the OSIRIS-REx mission, and we have not one but two new papers today.
First up, in a new paper published in the journal Science Advances, a team of scientists characterized the layer of rock just below Bennu’s surface. They found that this layer is, as expected, loosely bound rock bits. They also found that this layer contains twice the void space as the overall asteroid. Lead author Kevin Walsh explains: The low gravity of rubble-pile asteroids such as Bennu weakens its near-subsurface by not compressing the upper layers, minimizing the influence of particle cohesion. We conclude that a low density, weakly bound subsurface layer should be a global property of Bennu, not just localized to the contact point.
Many of our community will recall that the Touch-and-Go portion of the mission did more than just “boop” our rocky little asteroid. The sampling arm actually plunged about half a meter into the asteroid itself, basically because of all that loose rock and void space. Not only that, but images taken by an onboard camera revealed the displacement of a 40-centimeter rock.
Oh, and that sample collection left behind a 9-meter-long elliptical crater. More on that research can be found in a companion paper published in the journal Science.
The rubble pile nature of asteroids like Bennu and the Hayabusa2 target Ryugu presented scientists with a new mystery to solve. Before the arrival of those two missions at their targets, astronomers expected to see a relatively smooth and dusty surface, sort of like our Moon. Instead, they found tons and tons of small rocks and boulders and dust… so many rocks and boulders. But that dust was intriguing.