Unraveling the morphological and stratigraphic signature of global climate events within the Planum Boreum of Mars

Planum Boreum (PB) is a dome of layered icy material rising ~3 km above the surrounding plains in the northern hemisphere of Mars, and is divided into two main units: the lithic-rich basal unit (BU) and the overlying water ice-rich north polar layered deposits (NPLD). Since their discovery, the rich stratigraphic record of the NPLD has long been regarded as the key for understanding the most recent climate evolution of Mars and its dependency on periodical variations of Mars’ orbital parameters. The emplacement of the NPLD represents a major, global-scale shift of water ice on Mars, likely driven by climate change, yet the reasons and time scale for this event are still unknown. Similarly, the underlying BU likely recorded polar geologic processes and global climate in the Amazonian Period (3 Ga until present) in its strata and morphology, yet this unit remains largely unexplored. This is primarily due to limited outcrops of the lowermost NPLD and the underlying BU, as well as an incomplete understanding of the role of polar geologic processes in the context of global climate change. The large amount of remote sensing data acquired in recent years opens the possibility to better decipher the geologic record of PB with an integrated approach that couples radar sounding, high-resolution visible imagery and general circulation modeling. In this dissertation, I present three studies that take advantage of the extremely dense and extensive coverage of radar data over PB to map the lowermost NPLD and uppermost BU in their entirety, and integrate these with analysis of newly acquired high-resolution visible imagery of the BU-NPLD contact to reconstruct the transitional environment between the two units in great detail. These studies provide the observational constraints necessary to run general circulation models specifically tuned to the north polar region of Mars, and test their sensitivity to predicted Mars’ varying orbital parameters. This approach has the unique potential to determine which driving forces and geologic processes are responsible for the initial emplacement of the largest water ice reservoir in the northern hemisphere of Mars.Geological Science