We will carry out computer-based simulations of the spin-evolution of small near-earth asteroids (neas) in response to external rotational torque, such as delivered by the yorp radiation-recoil…

This federal contract award, valued at $390,286.00, was granted to the University of Maryland, College Park by the National Aeronautics and Space Administration (NASA) to carry out computer-based simulations of the spin-evolution of small near-Earth asteroids. The goal is to realistically model the response of aggregate asteroids to rotational stresses in order to interpret observational data and determine the strength parameters of these objects. The project aims to address key unanswered questions about the internal structure and evolution of near-Earth asteroids, including the formation of top shapes and binary companions. This award does not have a set-aside designation and is part of NASA's broader research program focused on asteroids and planetary defense. The University of Maryland, College Park is the prime contractor, and the work will be performed at their campus in College Park, Maryland.

We will carry out computer-based simulations of the spin-evolution of small near-earth asteroids (neas) in response to external rotational torque, such as delivered by the yorp radiation-recoil effect. Our goal is to simulate realistically the response of aggregate asteroids to rotational stresses, in order to build the theory that will enable the interpretation of spin data and allow US to translate the observations that are becoming available into actual strength parameters. The asteroids will be modeled as aggregated rocky fragments using a new multi-contact physics code that includes optional cohesion between the fragments. Asteroids in the gravity, weak-gravity, and strength regime will be studied in order to bracket the observed transition between larger, spin-limited asteroids and smaller, fast rotators. A thermophysical model of the yorp torque will be employed to provide self-consistent spin and shape evolution. High-level analysis products will include the range of physical model parameters that give rise to the surprisingly common top-shapes seen in the NEA population, including any centrifugal mass shedding and binary formation; self-consistent yorp evolution tracks for hundreds of cases using realistic contact physics; and animations detailing the shape evolution of selected simulations that illustrate the most important evolutionary processes. This project is aimed at advancing the state of knowledge regarding the internal structure (strength) of small neas. Compared to the increasing rate of discovery, physical characterization of neas lags far behind. The best way to probe the strengths of near-earth asteroids, short of launching space missions (which are very limited in choice of target and carry high risk), is to study their spin states and the equilibrium configurations to which they have evolved as a result of their spin histories. Our research will provide a theoretical understanding that will allow US to connect strength parameters to spin histories and present-day observables. Specifically, we will address the following currently unanswered questions regarding neas: (1) what material properties are necessary to permit the yorp-driven creation of KM-scale top shapes and allow for the formation of binary companions by centrifugal mass shedding? (2) what is responsible for the abrupt cutoff in the fast-rotator population, and why are there virtually no 500-meter fast rotators, contrary to theoretical expectations? (3) what is the expected distribution of small near-earth asteroid spin observables as a function of size resulting from self-consistent evolution under the influence of yorp?