Geologic control of jet formation on Comet 103P/Hartley 2

The EPOXI mission flyby of Comet 103P/Hartley 2 revealed numerous discrete dust jets extending from the nucleus, thereby providing an unprecedented opportunity to visually connect these features to the nuclear surface. The observed distribution of jets yields fresh insight into the conditions under which these cometary features may form. This study examines the geomorphology associated with areas of jet activity and then applies observed topographic correlations in the construction of a 2-D hydrodynamic model of a single dust jet. Visible light images of Hartley 2 show correlations between specific surface structures with both narrow-angle and fan-shaped dust jets; associations include pits, arcuate depressions, scarps, and rimless depressions. Notably, many source regions for jets appear finer than the practical mapping resolution of the imaging instruments (∼12 m). This observation indicates that the processes controlling jet formation operate at significantly finer scales than the resolution of most cometary activity models and motivates a complementary numerical investigation of dust jet formation and evolution. In order to assess controlling variables, our parametric numerical study incorporates different geometries and volatile abundances for the observed source regions. Results indicate that the expression of jet activity not only depends on local topography but also contributes to the evolution and development of surface features. Heterogeneous distributions of volatiles within the nucleus also may contribute to differences in local styles of jet activity.