High-resolution thermal inertia mapping from the Mars Global Surveyor Thermal Emission Spectrometer

High-resolution thermal inertia mapping results are presented, derived from Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) observation s of the surface temperature of Mars obtained during the early portion of t he MGS mapping mission. Thermal inertia is the key property controlling the diurnal surface temperature variations, and is dependent on the physical c haracter of the top few centimeters of the surface. It represents a complex combination of particle size, rock abundance, exposures of bedrock, and de gree of induration. In this work we describe the derivation of thermal iner tia from TES data, present global scale analysis, and place these results i nto context with earlier work. A global map of nighttime thermal-bolometer- based thermal inertia is presented at 1/4 degrees per pixel resolution, wit h approximately 63% coverage between 50 degreesS and 70 degreesN latitude. Global analysis shows a similar pattern of high and low thermal inertia as seen in previous Viking low-resolution mapping. Significantly more detail i s present in the high-resolution TES thermal inertia. This detail represent s horizontal small-scale variability in the nature of the surface. Correlat ion with albedo indicates the presence of a previously undiscovered surface unit of moderate-to-high thermal inertia and intermediate albedo. This new unit has a modal peak thermal inertia of 180-250 J m(-2) K-1 s(-1/2) and a narrow range of albedo near 0.24. The unit, covering a significant fractio n of the surface, typically surrounds the low thermal inertia regions and m ay comprise a deposit of indurated fine material. Local 3-km-resolution map s are also presented as examples of eolian, fluvial, and volcanic geology. Some impact crater rims and intracrater dunes show higher thermal inertias than the surrounding terrain; thermal inertia of aeolian deposits such as i ntracrater dunes may be related to average particle size. Outflow channels and valleys consistently show higher thermal inertias than the surrounding terrain. Generally, correlations between spatial variations in thermal iner tia and geologic features suggest a relationship between the hundred-meter- scale morphology and the centimeter-scale surface layer. (C) 2000 Academic Press.