Solar radiation produces a small force acting on solar system objects. Small asteroids are usually irregularly shaped, and the total force induces a torque on them and thus changes their spin…

This is a grant award from the National Aeronautics and Space Administration (NASA) to Auburn University, a public land-grant research university in Alabama, with a ceiling value of $279,575.00. The purpose of the grant is to quantify the evolution of the YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect, which is a small force acting on solar system objects like asteroids, and its impact on the rotational acceleration and shape deformation of irregularly shaped asteroids. The research will use a combination of computational modeling techniques, including finite element analysis and discrete element methods, to provide a comprehensive understanding of the dynamical and structural evolution of small asteroids. This grant is categorized under the NASA Solar System Workings (SSW) program, which supports research into the dynamical, geologic, and geophysical processes occurring on minor bodies in the solar system. The award does not have a set-aside designation.

Solar radiation produces a small force acting on solar system objects. Small asteroids are usually irregularly shaped, and the total force induces a torque on them and thus changes their spin conditions. This effect, a so-called yorp effect, is one of the critical elements that have generated the currently observed population of asteroids in the inner solar system. Studies have shown that the yorp effect can spin these asteroids up to their spin limits and change their shape configurations. Because the yorp effect is highly dependent on the shapes and material conditions, such deformation processes may cause the yorp effect to behave stochastically [cotto-figueroa ET AL., APJ 2015]. However, recent works pointed out that detailed analyses would be able to remove the stochastic trend of the yorp effect and provide a comprehensive understanding of the dynamical and structural evolution of small asteroids [e.g., mcmahon, DPS 2017]. In this project, we quantify the evolution of the yorp-driven rotational acceleration and shape deformation of irregularly shaped asteroids. We approach this issue by using a plastic finite element model (FEM) technique, a soft-sphere discrete element method (ssdem), and a yorp-coefficient computation technique. To quantify detailed interactions between the yorp effect and shape deformation, we will apply an efficient scheme in which the members can work separately. This project will use two key physical parameters that describe cohesion of geological materials and surface modification to characterize the yorp-driven spin-up. Using four publicly available polyhedron shape models, we analyze their realistic evolution processes to provide a quantitative framework and clear understanding of the yorp evolution of small asteroids. The answers derived in this project shed light on the structural and orbital evolution of small asteroids, giving critical hints on the origin of the solar system. Our work is categorized in (i) interior structure and (II) evolution and modification of surfaces in surface interiors. The SSW program supports research into dynamical, geologic, and geophysical processes occurring on minor bodies in the solar system. This program also encourages interdisciplinary efforts to solve key scientific questions. The NASA strategic plan states the importance of (1) expanding the frontiers of knowledge, capability, and opportunity in space and (2) ascertaining the content, origin, and evolution of the solar system. Our research fits the goals of the SSW program and the NASA strategic plan.