Glacial deposits, remnants, and landscapes on Amazonian Mars: Using setting, structure, and stratigraphy to understand ice evolution and climate history

Significant amounts of ice are located on the surface and in the subsurface of Mars. These polar and non-polar deposits are primarily water ice but, at the poles, carbon dioxide (CO2) ice exists on the surface where it exchanges seasonally with the atmosphere, while buried CO2 ice deposits have also been found. Analogous to Earth, Martian glacial ice deposits, as well as glacial remnants and landscapes from past glaciations, record how volatiles and components in the atmosphere, surface, and subsurface have interacted over time. Surface and subsurface expressions of past glaciations and deglaciations are critical to our understanding of the past climate on Mars, which is one of the highest priority goals in Mars science.

Mars’ ice and climate record is constrained by the glacial record that extends over the last ~1 billion years of the Amazonian Period. Imagery, elevation models, radar, and spectral data have revealed aspects of the setting and structure of glacial deposits, glacial remnants, and geomorphological signatures of receded glaciers. The stratigraphy of these landforms has the capacity to provide the most highly resolved record available of past climate conditions on Mars. We discuss three key questions, leading with: what history of the Late Amazonian Epoch climate is recorded in the Polar Layered Deposits? Then, what sequence of glaciation and deglaciation developed non-polar glacial remnants? Related to interpreting glacial landscapes, we discuss: how widespread were past warm-based conditions among extant Amazonian-aged buried glaciers? Addressing these questions is necessary as part of continued efforts to advance our understanding of ice and climate histories on Mars.