Origin and evolution of volatiles on Mars

In this thesis, we examine the nature of the observable volatile inventory in regolith and atmosphere of Mars in an attempt to explain the observed features on the martian surface. We explore this area using various techniques to explain the origin and temporal evolution of water reservoirs on both long and short timescales. The use of a simple analytic model is employed to demonstrate the ability of impacts to contribute to a planet's volatile inventory under certain circumstances, and to erode these volatiles under other conditions. Given an initial state of volatile abundance on Mars, we then use a general circulation model to study the redistribution of volatiles on the martian surface for varying orbital states, including changes in obliquity, eccentricity and argument of perihelion. We use, for the first time, a regolith model embedded within a full general circulation model to trace the flux of water into and out of the martian surface. Lastly, we examine the role of enhanced water vapor abundance in the atmosphere during high obliquity periods by introducing a new radiation scheme that will permit absorption and scattering by multiple gases, dust and cloud ice. We find that during conditions of high obliquity, surface ice is preferentially deposited at low latitudes, and regolith ice approaches the surface, confirming earlier suggestions. Over obliquity cycles, the regolith acts to retard the deposition of surface ice, and dictates, based upon its thermophysical properties, the locations where ice is preferentially deposited and/or retained. These locations correlate well with findings by the Mars Odyssey GRS instrument. Increased water vapor in the high obliquity atmosphere will generate noticeable greenhouse warming, further moderating the amount of surface ice deposited.