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Coupled Boulder Motion and Spin Evolution through the YORP Effect

Presentation #310.05 in the session Asteroids: Dynamics (Oral Presentation)

Published onOct 23, 2023
Coupled Boulder Motion and Spin Evolution through the YORP Effect

The YORP effect is a dominant influence on rotational acceleration for small bodies of diameter less than one kilometer. It’s magnitude and direction is highly sensitive to small features of the surface, therefore a greater degree of resolution is necessary for accurate predictions of future dynamics of these bodies. Models of surface roughness and feature contributions to YORP have advanced to prove that slight changes in shape can induce large changes in YORP [1]. It is also a culprit for the prevalence of young material surfaces for near-Earth objects which do not have extensive collisional histories [2]. Surfaces of asteroids may change in predictable ways according to the material properties and current spin-state dynamics, and boulder motion can be modeled as granular dynamics as well as discrete geometric boulders atop mesh surfaces [3][4]. The work presented here will apply boulder-induced YORP torque which, through rotational acceleration, will change the gravitational field of the surface and induce boulder motion and regolith piling. This coupled interaction will be examined for exhibiting either a strengthening or dampening effect on YORP spin coefficients over long timescales. Illustrating the YORP effect will advance model prediction of long-term spin evolution and provide a better understanding of the dynamical outcomes for small bodies. This modeling can also be used to characterize the stochastic nature of YORP and provide uncertainty bounds in the dynamics through simulation of real boulder behavior.

[1] Rozitis, B., & Green, S. F. (2011). Directional characteristics of thermal-infrared beaming from atmosphereless planetary surfaces - a new thermophysical model. Monthly Notices of the Royal Astronomical Society, 415(3), 2042–2062. [2] DeMeo, F. E., Marsset, M., et al. (2023). Isolating the mechanisms for asteroid surface refreshing. Icarus, 389(May 2022), 115264. [3] DeMartini, J. V., Richardson, et al. (2019). Using a discrete element method to investigate seismic response and spin change of 99942 Apophis during its 2029 tidal encounter with Earth. Icarus, 328(December 2018), 93–103. [4] Brack, D. N., & McMahon, J. W. (2019). Modeling the coupled dynamics of an asteroid with surface boulder motion. Icarus, 333(January), 96–112.

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