Impact cratering of icy and rocky targets in planetary sciences and in the laboratory

A review of impact phenomena past and present in the solar system is presented. The particular aim of this paper is to integrate impacts on icy surfaces alongside the traditional impacts on rocky surfaces. The data are given ordered in terms of the parent solar system bodies, thus are related to solar system bodies of different mass, density, gravity, orbital velocity, and surface composition. The results of some of the most interesting impact events and the impact structures recorded on the surfaces of various bodies are presented in tables. It is shown that a synthesis of impacts on ice and impacts on rocky surfaces is a natural thing to do. Crater structures and the consequences of impacts are common to both materials. There is thus no logical reason, other than past practice, to ignore one type of target material (ice) when discussing impact craters in the solar system. In addition to structures on planetary scales, we survey laboratory experiments with icy targets. It is shown that in recent years this previously relatively neglected area of study has developed rapidly. There is now much data available, under a wide range of conditions, for hypervelocity impacts onto ice in the laboratory. Finally, a new area of impact cratering can be identified, namely that into small solar system bodies such as asteroids and comet nuclei. In the latter case, impact cratering in porous, inhomogeneous ices still needs to be better understood.