Morphological Forms of Cometary Activity

The flyby of comet 103/P Hartley 2 (A'Hearn et al. Science 332, 1396 (2011)) revealed different kinds of activity from morphologically different areas of the nucleus. The small end spewed out icy grains most probably driven by CO2. Here mounds could be seen near the limit of resolution (Thomas et al. Icarus 222, 550 (2013)). Water sublimation is enhanced over a large smooth area between the sub nuclei. Some water ice is found on the surface near the dawn terminator. First images of the nucleus of comet 67/P Churyumov-Gerasimenko show a comparable multitude of surface morphologies. We expect that we can study the various forms of activity during the approach and rendezvous.