Dust in the Solar System

Eberhard Grün Max-Planck-Institut für Kernphysik, Postfach 103980, D-69117 Heidelberg, Germany

Interplanetary dust is the small-size tail of the meteoroid distribution which itself continues seamless into even bigger objects populations, i.e asteroids and comets. Interplanetary bodies are genetically connected via mutual collisions that results in cratering and fragmentation. There is a continuous flow of matter from bigger meteoroids into smaller ones. The collisional life times depend on the size of the objects and on the distance from the sun (e.g. mm-sized meteoroids will be collisionally disrupted at 1 AU within about 10,000 years). Transport of meteoroids in space by the Poynting-Robertson effect becomes increasingly more important for smaller meteoroids. The life times of micrometeoroids with sizes smaller than about 0.1 mm are determined by the Poynting-Robertson effect which causes them to spiral towards the sun and to sublimate before they
can be destroyed by a collision. Contrary to bigger meteoroids which are controlled by gravitational interactions dynamics of submicron-sized particles is dominated by radiation pressure and by electromagnetic interactions with the interplanetary magnetic field. Three distinctly different populations of dust particles have been identified in the solar system which contribute to the interplanetary meteoroid complex. In the inner solar system, out to about 3 AU, zodiacal dust particles orbit the sun on low inclination (i < 30 deg.) and moderate eccentricity (e < 0.6) orbits. Their spatial density falls off with approximately the inverse of the solar distance. Their sources are comets and asteroids. Interstellar grains of about 10-13 g in mass dominate in the outer solar system. It is found that these interstellar dust grains penetrate the solar system undepleted at least down to 1.3 AU from the sun and that they contribute about 30% of the total dust flux observed there. Periodic streams of tenth-micron sized dust particles originating from within the jovian system have been observed within a distance of about 2 AU from Jupiter.