Physics of interplanetary and interstellar dust

Observations of dust in the solar system and in the diffuse interstellar medium are summarized. New measurements of interstellar dust in the heliosphere extend our knowledge about micron-sized and bigger particles in the local interstellar medium. Interplanetary grains extend from submicron- to meter-sized meteoroids. The main destructive effect in the solar system are mutual collisions which provide an effective source for smaller particles. In the diffuse interstellar medium sputtering is believed to be the dominant destructive effect on submicron-sized grains. However, an effective supply mechanism for these grains is presently unknown. The dominant transport mechanisms in the solar system is the Poynting-Robertson effect which sweeps meteoroids bigger than about one micron in size towards the sun. Smaller particles are driven out of the solar system by radiation pressure and electromagnetic interaction with the interplanetary magnetic field. In the diffuse interstellar medium coupling of charged interstellar grains to large-scale magnetic fields seem to dominate frictional coupling of dust to the interstellar gas.