2005 Fall AGU Invited Abstract

Mars Surface Heterogeneity From Variations in Apparent Thermal Inertia. N. E. Putzig and M. T. Mellon, Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309.

Current techniques used in the calculation of thermal inertia from observed brightness temperatures typically assume that planetary surface properties are uniform on the scale of the instrument’s observational footprint.  Mixed or layered surfaces may yield different apparent thermal inertia values at different seasons or times of day due to the nonlinear relationship between temperature and thermal inertia.  To obtain sufficient data coverage for investigating temporal changes, we processed three Mars years of observations from the Mars Global Surveyor Thermal Emission Spectrometer and produced seasonal nightside and dayside maps of apparent thermal inertia.  These maps show broad regions with seasonal and diurnal differences as large as 200 J m-2 K-1 s at mid-latitudes (60ºS to 60ºN) and ranging up to 600 J m-2 K-1 s or greater in the polar regions.  Comparison of the maps with preliminary results from forward-modeling of heterogeneous surfaces indicates that much of the martian surface may be dominated by (1) horizontally mixed surfaces, such as those containing differing proportions of rocks, sand, dust, duricrust, and localized frosts; (2) higher thermal inertia layers over lower thermal inertia substrates, such as duricrust or desert pavements; and (3) lower thermal inertia layers over higher thermal inertia substrates, such as dust over sand or rocks and soils with an ice table at depth.

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