A Solar System dust ring with the Earth as its shepherd

Bodies orbiting in the gravitational fields of galactic, solar or planetary systems often suffer dissipative forces, including tidal interactions and drag resulting from motion through a gas or from collisions with dust grains. In the early solar nebula, gas drag induces resonance trapping, which may be of importance in the early accretional growth of planets^1-3. By means of numerical integrations, we show here that small dust grains can be temporarily captured into exterior orbit-orbit resonances with the Earth, lasting from less than 10,000 years to more than 100,000 years. Grains with radii of 30-100 µm, orbiting in planes less than 10° from the plane of the Solar System and with orbital eccentricities of less than 0.3, are captured most easily. We argue that there should be an approximately toroidal cloud of particles, derived mostly from the asteroid belt, trapped into a variety of these exterior resonances. The cloud is mostly beyond the Earth's orbit, but includes it.