This research focuses on the general circulation and climate system of Mars. There have been 7 successful spacecraft missions to Mars in the past 10 years returning valuable new data about the thermal structure of the atmosphere, the seasonal cycles of dust, water, and carbon dioxide, and the nature of the surface and subsurface. Our group interprets these data using a Mars General Circulation Model. We use the model to simulate the observations and determine what physical and dynamical processes are responsible for them. The model includes a full surface heat budget, a cloud microphysics package, a two-stream radiation code for gases and aerosols, a level-2 boundary layer scheme, mass conserving tracer transport algorithms, and CO2 condensation/sublimation physics. Topics we are currently studying include coupling between the present day dust, water, and CO2 cycles, the effect of orbital changes on past climates, and the nature of the early Martian atmosphere when surface pressures were thought to be higher than they are today. The goal of this work is to understand how the Martian atmosphere and climate system have evolved through time. Deadline: Feb 1, 2009 http://fellowships.hq.nasa.gov/gsrp/research/detail.cfm?oppID=33