Analysis of the sunward continuum features of Comet 103P/Hartley 2 from ground-based images

The analysis of continuum images of Comet 103P/Hartley 2 taken at the Kitt Peak National Observatory in 2010 is presented. Two distinct near-radial sunward continuum features were observed in the comet in November, while one sunward continuum feature is identified in images from October and December, 2010. The morphology and spatial extent of the continuum features are vastly different from the CN features. Radial spatial profiles of the continuum features were derived and at least some show a ρ−1 dependency, where ρ is the sky-plane projected distance from the nucleus. The range of observed position angles of the continuum features places constraints on the possible rotation models, if the features originate from specific fixed locations on the surface. Based on the observing geometry and the position angles of the continuum features, we deduced that the source regions of these continuum features cannot be located precisely at the end of the long axis (i.e. they cannot be parallel to the long axis of the nucleus), but the curvature of the surface is so large at the small lobe that the source could still be on that lobe. The progression of the continuum feature in images from November 5 yields a lower limit for the grain velocity V of the order of 0.08 km s−1. The maximum sunward extent of the continuum features constrains V2/β, where β is the ratio of the radiation pressure force to the gravitational force due to the Sun.