Constraining Water Volume in the Gypsum Sands of the Martian North Polar Erg

The Martian geologic record contains abundant evidence for the presence of surface liquid water in the past, however, the fate of this liquid water is not well constrained. One mechanism to sequester this water is within the crystal structure of minerals, such as gypsum (CaSO₄*2H₂O), which both contains structurally bound water and requires liquid water to form.  Olympia Undae, also known as the North Polar Erg, is the largest dune field on Mars, and is known to contain gypsum sands. These gypsum dunes are a reservoir for water that has not been accounted for in Mars' water budget. As the amount of water stored in the gypsum dunes is currently unknown, the water budget for Mars' northern polar region is not well constrained.

Our study combines orbital data from several instruments onboard the Mars Reconnaissance Orbiter, specifically visible near-infrared (VNIR) data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), images from the Context Camera (CTX), and digital terrain models (DTMs) from the High-Resolution Imaging Science Experiment (HiRISE), to help constrain the amount of water bound in the Olympia Undae gypsum dunes. These remote-sensing data sets are supplemented by ground truth results  from White Sands National Park, New Mexico, USA, which contains the largest gypsum dune field on Earth. By combining these different data sets and leveraging in-situ measurements from a terrestrial analog, the water content of the entire north polar erg will be quantitatively estimated and contextualized. This investigation will improve our constraints on the Martian volatile budget, and the processes that have contributed to the sequestration of water on Mars.