On the source and structure of interplanetary dust particles

Cometary dust grains measured by the Halley space missions show a silicate- and a light element component. The latter most likely represents an organic material. Grain density is mostly below 1 g/cm3. The organic component slowly decays at higher temperatures during subsequent perihelion passages. Therefore ''older'' cometary grains differ from the ''young'' cometary grains: they show higher albedos, higher densities and orbit finally within the inner solar system. (author). 19 refs