USING SURFACE TEMPERATURES TO INTERPRET SEDIMENTS AND VOLATILES AT MARS ANALOG SITES

Satellite-derived surface temperatures have been a valuable tool for geologic mapping since the first deployments of thermal infrared imagers to Earth orbit and Mars in the 1970s. Special attention has been given to the utility of these datasets for identifying hazards to landers and rovers and for detecting subsurface volatiles for in situ resource utilization. However, efforts to quantify the physical properties and volatile abundances of rocks and sediments using thermal data have consistently yielded large uncertainties. Combinations of grain size, packing geometry, cementation, volatile abundance, subsurface heterogeneity, and sub-pixel horizontal mixing lead to multiple scenarios that would produce a given thermal response at the surface. Recent developments in UAS-supported infrared imaging tools enable a new era for experimental analysis of the role of a diverse suite of geologic materials in dictating heat transfer, which has been historically difficult to model or simulate in laboratories. We use Mars-analog settings on Earth as natural laboratories for studying how the interplay of these traits control diurnal temperature curves. We completed 8 field campaigns in the last year to sites around the US Southwest, Hawai’i, and Iceland, each providing a unique sedimentary endmember for constructing an inclusive model. At each site we deployed a modular weather station that constrains the surface energy flux with minute-interval data and allows us to calibrate free model parameters to observed surface temperatures and measured soil thermal inertias. Then, using data captured from a UAS, we model surface and subsurface thermal conductivity of numerous material types in 1000s of m² field areas. By pairing model results with multispectral imagery and systematic sample analysis, we are able to identify how combinations of key thermophysical controls, including soil moisture, grain size and shape, cementation, and composition, dictate the thermal response in different environmental contexts. This study relates features that can be diagnostic of specific weathering and alteration regimes to properties that can be measured from orbit, thereby improving the capabilities of thermal infrared remote sensing data in uncovering past environmental settings and identifying near-surface resources.