Presentation #212.08 in the session MBAs: Physical Characteristics (iPosters).
The YORP (Yarkovsky–O’Keefe–Radzievskii–Paddack) effect, induced by the asymmetrical recoil force of the thermal irradiation from the surface of an asteroid that absorbs the energy of the solar radiation, may alternate the asteroid’s spin rate and obliquity of pole. The YORP effect depends on the thermal and dynamical parameters and the shape of the asteroid in a very complicated way, thus general quantitative conclusions of this effect are currently rare. In this poster, we present our exploration on YORP effect using a toy model, which is a spherical asteroid decorated by craters and boulders. The temperature distribution on the surface is numerically calculated in three dimensions using the software Multiphysics COMSOL and taking into account of the shadowing and thermal re-illumination effects. The YORP torque arising from the temperature distribution is calculated and averaged over the rotation and revolution periods. We find that the equilibrium state of the spinning asteroid and the change rates of spin frequency and obliquity depend on the size, location, and shape of the craters and/or boulders. Especially, some asymmetrical equilibrium obliquity values (other than 0, 90 and 180 degrees) are found for asteroids with craters on certain latitudes. These results can be used to assess the YORP effect on irregularly shaped asteroids, since an arbitrary shape can be approximated by a combination of a certain number of such toy asteroids.