Morphology of the Planum Boreum basal unit, Mars, and constraints on the origin and timing of icy circumpolar deposits

• Main Author: Brothers, Thomas Charles
• Other Authors: Holt, John W., Ph. D., Wood, Lesli J, Tanaka, Kenneth, Kocurek, Gary A, Mohrig, David
• Format: Thesis
• Language: English
• Published: 2015
• Subjects: Mars; Polar science; Ice deposition; Planum Boreum; North Pole; Ice cap
• Online Access: http://hdl.handle.net/2152/32615; https://doi.org/10.15781/T2NH04

text Data from the Shallow Radar instrument on Mars Reconnaissance Orbiter have enabled detailed scientific exploration of martian ice. Orbital ground penetrating radar enabled scientists to study subsurface ice stratigraphy, to uncover the geologic structure of ice on Mars with remarkable results for the north pole. On the north pole of Mars sits a massive, approximately two kilometer thick, deposit of pure water ice. This deposit is underlain with a sand and ice mixture that reaches 1.5 km maximum thickness. This dissertation examines the nature of the old sand/ice mixture on Mars' north pole. We use this ice to identify early trends in deposition and erosion on Mars' north pole and ultimately to link ice rich deposits that are not part of the polar cap. This multi-part study endeavors to understand and constrain the drivers of Mars' polar ice deposition. With careful stratigraphic analysis we hypothesize that depositional regime has not changed drastically since the upper part of the sand and ice mixture was emplaced in Middle Amazonian time. Sediment supply became limited and ice more plentiful with respect to sand; however, deposition remained aeolian in nature. Additionally, our work finds evidence that circumpolar landforms are related to the central mass of ice on Planum Boreum. We present evidence supporting a coeval evolution of the circumpolar deposits and central Planum Boreum. We also present evidence that refutes these features being part of a more extensive ancient ice cap. This indicates that the processes occurring at Planum Boreum are likely mirrored in nearby landforms such as small craters and isolated ice wedges. This is fundamental to polar science, the processes occurring on Planum Boreum and the processes responsible for deposition of the north polar layered deposits can be analyzed at additional locations. Furthermore, we find that if a climate signal exists in the ice deposits, as has been postulated, these circumpolar features are likely to contain the same climate signal as the central ice cap. Thus, this work unifies the complexity of martian polar processes and suggests future avenues of research. Geological Sciences