[PPS04-09] Global Geology of Bennu from NASA's OSIRIS-REx Space Mission
Keywords:Rubble Pile Asteroids, Asteroids, Craters
The population of boulders is diverse, with many of the largest boulders being darker than the average surface albedo and exhibiting a hummocky texture. A smoother and brighter class of boulders occurs at smaller sizes, and the populations are mixed throughout the surface. Notably there is a distinct lack of very large boulders in the equatorial region (+/– 25 deg.). Only 2 of the 16 boulders larger than 30 m are located in this band. Patterns of apparent mass movement across the surface suggest movement from the mid-latitudes towards the equator. There is evidence of imbrication in the local downslope direction, as well as evidence of mass movement at smaller particle sizes in the form of partial burial of boulders and pileup of boulders at locations downslope of scarps. Many of these signatures are found specifically in regions with high surface slope and in regions where the surface slope would have increased substantially as the asteroid experienced its observed increase in spin rate. The spatial distributions of craters, boulders, observed particle ejection events and signatures of mass movement suggest a dynamic recent history in some regions of Bennu’s surface, and we use these data to divine information about the most mobile elements of its surface and their? relation to the history of Bennu’s equatorial ridge.