Shallow Ice Detection on Mars: Integration of Thermal and Neutron Datasets into the Mars Subsurface Water Ice Mapping (SWIM) Project

Abstract:

There has been long-term interest in the detection and characterization of shallowly buried ice on Mars, driven by climate science and human exploration goals. The Subsurface Water Ice Mapping (SWIM) project supports ongoing efforts by NASA’s Mars Exploration Program to determine in situ resource availability for human missions. The SWIM project leverages the full suite of ice-sensitive datasets to give an integrated view of ice availability in the upper 10s of meters of the Martian subsurface, specifically using geomorphological analysis and a new radar surface return technique to bridge the sensing-depth gap between the shallow geophysical data sets (thermal data and neutron spectroscopy; < 1 m) and deep radar reflectors (SHARAD; > 20 m).

Precise knowledge of ice-table depth is critical for human landing site selection as a metric of mechanical accessibility. At the 2020 AGU Fall Meeting, we will present new analysis of ice-table depth datasets derived from the MGS Thermal Emission Spectrometer (TES), the MRO Mars Climate Sounder (MCS), and the Mars Odyssey Neutron Spectrometer (MONS), and integration of these datasets into the SWIM project. Our analysis includes new TES layer heterogeneity maps produced for the SWIM project, which we compare to TES/MCS/MONS ice-table depth maps previously produced by Bandfield & Feldman (2008), Piqueux et al. (2019), and Pathare et al. (2018), respectively.

We have made detailed comparisons between these four ice-depth products by (1) visually comparing maps, (2) building 2D histograms of map pairs, and (3) identifying 14 spot check locations for targeted thermal modeling and analysis of the relative performance of each mapping technique. We have referenced the Phoenix landing site and recent ice-exposing impact locations as approximate ground truth. We will present the results of our comparative depth analysis, as well as derived shallow ice resource maps produced via both weighted averaging and Bayesian techniques. We will discuss key uncertainties in the derivation of mid-latitude ice-table depths from orbit and implications for future landing site selection.