Investigation into the disparate origin of CO2 and H2O outgassing for Comet 67/P

Spatial radial profiles of H2O on April 27 on the illuminated side of the comet, extending from 1.78 to 6.47 km from the nucleus center, show that water follows model predictions quite well, with the gas accelerating as it expands into the coma. Our dayside radial profile allows us to make an empirical determination of the expansion velocity of water. On the night side the spatial profile of water follows 1/ρ. The CO2 profiles do not exhibit any acceleration into the coma but are closely matched by a 1/ρ profile.