Speaker
Description
The OSIRIS-REx and Hayabusa2 missions yielded a wealth of data that is transforming the understanding of rubble-pile asteroids, providing unprecedented insights into their composition, structure, and evolution. Rubble-pile asteroids are highly porous, loosely bound collections of rocks and boulders held together primarily by gravity, with minimal cohesion, and measuring less than a few kilometers in size [1]. The power-law distribution of asteroid sizes indicates that rubble-pile asteroids are the most common class of near-Earth asteroids, making them of significant interest for planetary defense initiatives [2]. However, there is limited data on gravity field measurements and observations for rubble-pile asteroids, and no measurements for sub-kilometer-sized asteroids exist aside from OSIRIS-REx and Hayabusa2 mission data [1]. Therefore, there is a significant gap in understanding the density distribution and surface and subsurface properties of rubble-pile asteroids, which limits the scope and success of future planetary defense initiatives involving rubble-pile asteroids.
This research focuses on developing a high-fidelity, component-based density model of asteroid Bennu, leveraging gravity field measurements and sample return data from the OSIRIS-REx mission. Initial work using a spherical model highlights significant density heterogeneity, including an under-dense core, an under-dense equatorial bulge, a dense subsurface layer, and a boulder-strewn surface regolith. Figure 1 illustrates these components and presents various core size configurations. The next step involves replacing the spherical model with a 3D shape model of Bennu and calibrating it to match the measured gravity coefficients obtained by OSIRIS-REx. Furthermore, granular mechanics simulations, implemented through the LMGC90 platform—a specialized tool for modeling granular materials and their interactions—will enable detailed investigations of vehicle interactions with Bennu’s surface and subsurface properties [3].
This work advances understanding of Bennu’s internal structure and provides a validated framework for modeling rubble-pile asteroids. These results will inform future planetary defense strategies and mission designs targeting rubble-pile asteroids, including those related to resource extraction and asteroid deflection.
References
[1] D. J. Scheeres, et al., Heterogeneous mass distribution of the rubble-pile asteroid (101955) bennu, Science Advances 6 (2020) eabc3350.
[2] E. B. Bierhaus, et al., A subsurface layer on asteroid (101955) bennu and implications for rubble pile asteroid evolution, Unpublished Manuscript (2023).
[3] P. Sanchez, M. Renouf, E. Azema, R. Mozul, F. Dubois, A contact dynamics code implementation for the simulation of asteroid evolution and regolith in the asteroid environment, Icarus 363 (2021) 114441.