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-Robertso n is a dissipative effect, thus making a particle subject to it spiral towards the Sun. For meter-sized bodies, Poynting-Robertson is too we ak to cause any observable effect. Another transverse force, also indu ced by radiation pressure, is dominant for this size range: the Yarkov sky effect. The idea behind the Yarkovsky effect is that re-emission o f 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 d irection to the hotter hemisphere. The Yarkovsky force can be dissipat ive 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 ast eroid fragments) subject to the Yarkovsky effect. We first solve the t ime-dependent heat conduction equation to offer a new deduction of the Yarkovsky effect. Then we present some examples of the dynamical evol ution of meter-sized bodies suffering dissipative and antidissipative forces. The dissipative force may confirm that many meteorites found o n the surface of the Earth have their origin in the combined effect of the Yarkovsky force and resonances with Jupiter. With the antidissipa tive force some good examples of trappings in resonances with Jupiter can be found, because in these cases the orbits are converging and cap ture is more natural.