P058-04
Mapping Martian ice availability in the mid-latitudes of Mars

Monday, 14 December 2020: 08:42
Virtual
Jennifer Buz, Northern Arizona University, Flagstaff, AZ, United States, Christopher S Edwards, Northern Arizona University, Astronomy and Planetary Science, Flagstaff, AZ, United States and Sylvain Piqueux, Jet Propulsion Lab, Pasadena, CA, United States
Recorded Presentation
Abstract:
Orbital and lander missions demonstrated that the high latitude regions of Mars have shallow subsurface ice. Recent studies using thermophysical modeling have shown that shallow ice is widespread in both the mid- and high-latitudes. This ice is critical for both understanding the history of volatile transport and for future mission planning and in-situ resource utilization.

The thermal inertia of massive or pore-filling water ice is particularly high, significantly altering seasonal surface temperature patterns. Using repeat observations taken by the Thermal Emission Imaging System (THEMIS) at different seasons enables high-resolution calculations of the thermophysical properties of the surface, in particular the thermal inertia, and the presence of subsurface ice. Furthermore, it is now possible to estimate the depth to any ice-rich layer found. Modification of previous ice depth calculation techniques for use with THEMIS and has enabled mapping at higher resolution than previously possible.

We use the KRC numerical thermal model in conjunction with a DaVinci Interface (krc.mars.asu.edu) for thermophysical calculations. A particular season, here called Ls*, exists where the surface temperature is primarily influenced by the top-layer thermal inertia. We use THEMIS observations during this season to calculate the thermal inertia of the dry surface layer above the ice (if any). We assume a two-layered geometry of dry basaltic soil on top of a water-rich layer. We then find, if possible, an overlapping THEMIS nighttime image acquired at ΔLs>100°. We use the band 9 (12.57 μm) brightness temperature of the THEMIS image acquired during Ls*, latitude, local time of observation, Ls, slope, albedo, dust opacity, elevation, and azimuth as inputs into the KRC thermal model to calculate the thermal inertia of the surface. We then generate a look-up table for surface temperatures during the season of the second image using ice depths ranging between 0.06 and 1.2 seasonal skin depths.

We find that thermal inertia and albedo are strong influences on ice depth and that ice depth varies significantly locally. These results will be necessary for future mission planning and in-situ resource utilization.

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