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Rossmann, Francis Marcel

University of British Columbia

Asteroid (101955) Bennu is a near-Earth, potentially hazardous asteroid and was the primary target of the NASA OSIRIS-REx mission. Bennu is a rubble pile asteroid: a highly porous, gravitationally bound aggregate of boulders, formed after the catastrophic disruption of its parent body. The asteroid’s rugged surface is dominated by the expression of boulders and has been heavily modified by impact cratering. Here, I analyze surface roughness, calculated using data from the OSIRIS-REx Laser Altimeter, to investigate spatial variations in boulders and fine-grained material across Bennu globally. Surface roughness is a statistical measure of change in surface height over a given baseline (horizontal spatial scale) and can be used to gain insight into the geologic processes that modify the surface over different scales. Here, I performed a surface roughness assessment of asteroid Bennu at baselines of 0.25 m to 25 m using the root-mean-square (RMS) deviation. Studies of surface roughness provide an excellent opportunity to compare asteroids for which detailed surface roughness analyses exist, and I compare my results with those of (25143) Itokawa and (433) Eros. I find that the surface roughness of Bennu is self-affine, spatially varying, and is dominated by the spatial density of boulders on the asteroid surface. A moderate statistical correlation was found between roughness and Bennu’s shape, most pronounced in the mid to high latitudes. At the longest baselines, I find that roughness is produced by the prominent equatorial ridge, the topographic relief of Bennu’s largest boulders, and occasionally by large boulders in local topographic minima such the interiors of large craters. At baselines between 0.25 m and 2.0 m, I find that the interiors of craters with diameters < 20 m to 25 m tend to be much smoother compared with bulk Bennu and larger craters, supporting the presence of a fine-grained subsurface layer.

Text

2024-01-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87331

Geophysics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/