| A substantial amount of evidence has accumulated over the past two decades for the presence and persistence of liquid water on the surface of Mars early in its history---from the oldest observable surfaces up to approximately 3.5 billion years ago. The presence of liquid water on modern Mars is possible only under peculiar circumstances, and for ancient Mars these circumstances are further limited by predictions of the Standard Solar Model that the Sun was significantly fainter at that time. Large asteroid and comet impacts have been suggested by Carr (1996) [95] and Segura et al. (2002) [403] as a possible triggers of warm and wet climate episodes early in Martian history. My goal is to model impacts into stratigraphically complicated media, specifically targets containing water ice in various morphologies, in order to determine a lower bound on the energy and size scales of impact events that could trigger such a climate shift, and thus establish an upper bound on the frequency of such events.;To do this, I used various analytical and numerical modeling techniques, including the RAGE hydrocode RAGE [292] is an Eulerian hydrocode that runs in up to three dimensions and incorporates a variety of equations of state including the SESAME tables maintained by LANL. In order to test the accuracy of RAGE predictions before applying it to the problem. I compare code results against analytical models (verification) and laboratory experiments (validation) that are related to the problem. Specifically, I compare RAGE against experiments ([392], [358]), and analytical crater scaling models ([226], [221], [218], and [322]). From there, I examine the potential effects of impacts on water ice in the Martian subsurface, first by examining the evolution of the temperature and pressure profiles of an impact into a geologically simple, ice-free target, and then exploring the effects of ice content and morphology. |
