MELTING PROBES AS A MEANS TO EXPLORE PLANETARY GLACIERS AND ICE CAPS

摘要

On many planetary bodies thick layers of frozen volatiles cover the surface. Examples are: The polar ice caps of Earth and Mars, consisting of H_O-ice and an mixture of H_2O- and CO_2-ice, respectively; Neptune's satellite Triton, whose polar areas are composed of nitrogen (N_2)-ice, and the icy satellites of Jupiter (in particular Europa), which most probably host liquid layers below their ice crusts. Access to deeper parts of the ice layers is of ultimate importance for understanding the climatological history of the respective bodies, as well as for exobiological aspects. Icy layers often "grow" continuously in the course of the planetary history - and thus should contain key information on the surface conditions in the past, including the possibility to find .remnants of extinct primitive live. In contrast to solid rocky surfaces (where the application of heavy and power-demanding drilling and hammering devices is the only possibility to access their interior), ice layers could be explored by much simpler means, namely melting probes. We review several concepts for such devices, the state of art in the development, and discuss possible applications for the exploration of the Mars polar areas. Estimates of the power consumption expected for such probes and the penetration speed are also given.