ASTEROID FRAGMENTS IN EARTH-CROSSING ORBITS

The dynamics of small bodies in the Solar System are ruled not only by gravitational forces but also by non-gravitational forces such as the Poynting-Robertson effect and the Yarkovsky effect. Poynting-Robertson is a dissipative effect, thus making a particle subject to it spiral towards the Sun. For meter-sized bodies, Poynting-Robertson is too weak to cause any observable effect. Another transverse force, also induced by radiation pressure, is dominant for this size range: the Yarkovsky effect. The idea behind the Yarkovsky effect is that re-emission of radiation from a rotating body is higher in the dusk hemisphere than it is in the dawn hemisphere, thus creating a force in the opposite direction to the hotter hemisphere. The Yarkovsky force can be dissipative or antidissipative making the body spiral, either converging to or diverging from the Sun, respectively. The purpose of this work is to better understand the dynamics of meter-sized bodies (for instance asteroid fragments) subject to the Yarkovsky effect. We first solve the time-dependent heat conduction equation to offer a new deduction of the Yarkovsky effect. Then we present some examples of the dynamical evolution of meter-sized bodies suffering dissipative and antidissipative forces. The dissipative force may confirm that many meteorites found on the surface of the Earth have their origin in the combined effect of the Yarkovsky force and resonances with Jupiter. With the antidissipative force some good examples of trappings in resonances with Jupiter can be found, because in these cases the orbits are converging and capture is more natural.