Clues to the structure of meteoroids, from dust to light scattering properties

Clues to the structure (compact or fluffy) of dust particles in meteor streams are provided through observations of solar light scattered by cometary and interplanetary dust particles. While their phase curves are mostly similar, and indeed characteristic of irregular particles, differences are noticed (both from remote and in-situ observations), mainly in terms of polarization levels and polarization colour. These differences suggest different formation regions, as well as an evolution of the dust morphological properties, linked to fragmentation and evaporation processes. Recent results, mainly from laboratory measurements, are presented. Significant polarization phase curves, obtained with the PROGRA² experiment, are presented for samples of terrstrial and meteoritic origin. Some results of the CODAG experiment, launched from Esrange in May 1999, are discussed. The significance of microgravity for light scattering measurements on low-density clouds is emphasized, together with the differences in polarization colour effects for compact particles and fluffy aggregates.