Characterizing Inter-Annual and Inter-Seasonal Dust Deposition and Removal on Mars Using Thermal Emission Imaging System (THEMIS) Infrared Data

Abstract

The current climate of Mars is characterized by frequent dust storms, during which dust is raised from the surface and transported throughout the atmosphere via global circulation and wind patterns. The addition or removal of dust can cause the surface to brighten or darken significantly. This process not only modifies the appearance of the surface, but alters the thermal insulation properties due to the low thermal conductivity of dust. Of particular interest is the inter-annual/seasonal pattern of dust redistribution and the spatial scales at which such process take place. While global climate models predict changes in surface dust coverage before and after global storms, their output concerning the amount and locations of transported dust differs significantly. Changes in both dust coverage and thickness are constrained by employing a numerical thermal model and analyzing surface temperature differences from overlapping Thermal Emission Imaging System-Infrared images. A multi-dimensional lookup table relating thermal inertia, surface temperature difference, and dust layer thickness is constructed to derive changes in surface dust redistribution at high spatial resolution for both inter-annual/seasonal timescales. Modeled surface albedos are also derived to provide an additional constraint on surface dust redistribution. Upper and lower limits for derived changes in surface dust thickness are established from variations in surface temperature and modeled surface albedo respectively. Upon analyzing two distinct image pairs, we find that dust deposition/removal can occur at small spatial scales (i.e., 100s of m) and that changes in surface dust thickness can range from a few to hundreds of microns.