Evolution of the obliquities for nine near-Earth asteroids

The evolution of the obliquities of nine near-Earth objects is investigated, using the method developed by Laskar and Robutel (Nature 361, 608–612, 1993). A comparison with a frequency analysis is also made. The evolutions of the orbital elements are irregular and often chaotic for all the objects, sometimes involving quite large and very fast occurring changes. The nine objects all experience chaos or have other large frequency-related zones for large intervals of initial obliquities, as opposed to the situation for the main-betl and Trojan objects that was examined in an earlier paper (Skoglöv et al., 1996).