High-resolution 3D radar mapping, analysis, and modeling of the internal layers within the north polar layered deposits (PB3Dv2A)

NOTE: In September 2024, Matt Perry moved from Science PI to PI, and Than Putzig became a Co-I.

We are conducting high-spatial-resolution radar mapping and stratigraphic analyses of Mars’ north polar layered deposits (NPLD) using the recently completed, publicly available second iteration of the Planum Boreum (PB) three-dimensional (3D) SHARAD radargram. We will accompany these analyses with physics-based numerical modeling of stratigraphic development over a large number of locations within the NPLD to determine the spatiotemporal variations of accumulation in the polar region. While localized studies investigating various phenomena throughout PB have been carried out, no prior effort to map all of the internal radar layers had been undertaken. Such an effort will facilitate a search for structural complexities that inform depositional and erosional mechanisms. Pairing radar-derived stratigraphy with formation modeling at fine spatial sampling will increase understanding of NPLD history and provide an unprecedented insight into the physical processes that created the layers. There remain many unanswered questions regarding the nature of the NPLD, notably those concerning its depositional history and structure. Paramount among these are 1) What do angular unconformities and trough migration patterns tell us about modification processes and the geomorphology of Planum Boreum? 2) What are the ages of the various layers within the NPLD, and how do they relate to the evolution of the Martian climate through geologic time? 3) What is the history of volatiles sublimating from the NPLD and being deposited at mid and low latitudes and vice versa? and 4) What flux of volatiles to and from Planum Boreum is represented by the physical expression of the layering that extends 100s to 1000s of meters below the surface?

To address these questions, we are carrying out three phases of research. Phase I involves detailed mapping of the numerous radar layers within the NPLD. This work includes delineation of the layer boundaries. In Phase II, we will interpret the internal structure of the NPLD. Using results from Phase I, we will identify a number of structural features including: unconformities and discontinuities such as cap-wide trough-migration paths to assist in interpretation of the spatiotemporal evolution of the cap; other buried features such as chasmata and other erosional and depositional features that have been difficult or impossible to map using standard 2D radargrams; and, where possible, any identifiable buried impact craters below and within the ice that may be used to determine relative accumulation rates of the internal layers. In Phase III, we will couple the high-resolution mapping results from Phase 1 with modeling of accumulation that results from atmospheric processes and orbital forcing. Due to the prohibitive computational complexity of modeling the entire cap at once, we will model the construction of portions of the NPLD at various locations to capture spatiotemporal variations. Following these modeling efforts, we will use statistical analyses to determine correlations and potential anticorrelations in the resulting model output.