P061-06
Stability Regions of Surface and Subsurface Polar Volatiles from Diviner Lunar Radiometer Data

Monday, 14 December 2020: 17:50
Virtual
Margaret E Landis, Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, Paul Ottinger Hayne, University of Colorado, Boulder, CO, United States, Jean-Pierre Williams, University of California, Los Angeles, CA, United States, Benjamin T Greenhagen, Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States and David A Paige, University of California Los Angeles, Department of Earth, Planetary, and Space Sciences, Los Angeles, CA, United States
Recorded Presentation
Abstract:
The polar regions of the Moon are of key future scientific and exploration interest because they are the most likely places to harbor volatiles, including water. The presence of water, sulfur, and organics within the polar regions may also record the variety and types of sources that have delivered volatiles to the Moon.

We use data from Lunar Reconnaissance Orbiter’s Diviner Lunar Radiometer in order to quantify the maximum and average surface temperatures from 60° - 90° latitude in both hemispheres, and to determine where different volatile species could be stable. We consider three volatiles of interest (sulfur, water, and hydrogen cyanide, in order of decreasing stability temperature) that may be key indicators of the contributions from different volatile sources (e.g., volcanic outgassing, solar wind sputtering, and cometary impacts). The regions we identify in Diviner data are regions where volatiles are thermally stable to losses of < 1 mm/Gyr based on the maximum surface temperature (surface stability) or annual average temperature and a vapor diffusion model (subsurface stability). Whether volatiles are actually present in these regions depends on the supply and destruction rates.

We find that there is roughly the same amount of subsurface area (~3 x 105 km2) where water ice could be stable at ~ 1 m depth in both hemispheres, while the surface stability area for water ice is significantly less in the northern hemisphere than in the south. If significant water ice was delivered to the lunar poles after the formation of the current topography, this may imply that less surface water ice was able to be buried over time at the north than the south.

We also looked for regions that were relatively accessible for future volatile sample return missions and that could host all three volatiles of interest. The relative quantity and stratigraphic relationships of sulfur, water, and cometary species (like hydrogen cyanide) on the surface would provide data to test hypotheses of volatile delivery to the poles. Of note is Amundsen crater, a relatively flat-floored complex crater centered at ~84.5° S, which hosts a relatively accessible region where all three volatiles of interest (if present) are stable close to the edge of the permanently shadowed region (PSR) within the crater.

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