Mars' Water Cycle Seen Through an Ice Len

The water cycle of Mars has been intensely studied thanks to data from orbiting spacecraft and landers on the surface. Water is of major interest due to its vital connection to life on Earth. The global cycle is driven by the planet's major source of water vapor, the north polar residual water-ice cap, and the amount of this vapor is very sensitive to polar insolation. Climate can be expressed in the behavior of water ice present at the surface, both seasonally and perennially. Here, I enhance our knowledge of Mars' current and recent climate by investigating the occurrence and physical structure of water ice at the surface with a combination of data analysis and numerical modeling.;In chapter 2 I analyze surface temperatures and albedo from broadband thermal-infrared and visible observations, in order to characterize the seasonal cycle of water frost. I identify extensive deposition of water ice in the northern hemisphere during autumn, whereas the southern hemisphere shows little evidence for water ice deposition. I argue this is a result of the configuration of major water sources at present (i.e., the primary source of water vapor being at the north pole).;In chapter 3 I analyze the stability of icy outliers of the northern polar cap of Mars with both high-resolution imagery and numerical models. These outliers are mounds of water ice ∼10-50 km in diameter, up to ∼2 km thick, and are not contiguous with the residual cap (the most-equatorward being at 70°N). They are potentially unstable, so secular changes in mound extent are explored using multi-year high-resolution images. I estimate the current annual mass balance using a coupled 1-D thermal and atmospheric model. Both lines of study support the outliers being close to equilibrium, suggesting, at present, surface deposits may equilibrate at the same pace as the changing orbit.;In chapter 4 I derive maps of thermophysical properties of the north polar residual cap itself with thermal models and binned temperature data. I investigate depth-density relationships in the polar water ice deposit and find that porous ice overlies a denser ice substrate, which could indicate recent accumulation. We find a noticeable difference between the interior and edge of the residual cap, supporting recent accumulation over the interior and ablation at the edges. The properties I derive will provide insight into the recent behavior of the martian north polar residual cap, which remains largely unknown.