Observations and models of the kinematics of the zodiacal dust cloud

We report on new observations of the motion of zodiacal dust using optical absorption line spectroscopy of zodiacal light. We have measured the change in the profile shape of the scattered solar Mg I lambda 5184 line toward several lines of sight in the ecliptic plane as well as the ecliptic pole. The variation in line centroid and line width as a function of helio-ecliptic longitude show a clear prograde signature and suggest that significant fraction of the dust follows non-circular orbits that are not confined to the ecliptic plane. When combined with dynamical models, the data suggest that the zodiacal dust is largely cometary, rather than asteroidal, in origin.