Mars surface thermal inertia and heterogeneities from OMEGA/MEX
Résumé
The thermophysical structure of the martian surface is the result of various processes that have shaped the martian surface through time. Previous dedicated heliosynchronous measurements of the thermal infrared (IR) flux of the martian surface have revealed the diversity of martian surface thermal properties, as well as its complexity linked to the heterogeneous nature of terrains. We present the first retrieval of thermophysical properties of the martian surface using near-infrared (NIR) Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) onboard Mars Express (MEX) thermal measurements from 5 to 5.1. µm. MEX orbit around Mars is elliptical and therefore OMEGA has performed surface temperature measurements at various local times and seasons over more than 4 full martian years. We have developed a method to exploit these unprecedented measurements using a one-dimensional energy balance code derived from a Global Climate Model that allows retrieval of the thermal properties of the martian surface using OMEGA data. Regional maps of the thermal inertia at a resolution up to 32 pixels per degree and a global map at 4 pixels per degree are presented. OMEGA-derived thermal inertia values agree with previous mappings by the Thermal Emission Spectrometer (TES) onboard Mars Global Surveyor (MGS) and Thermal Emission Imaging Spectrometer (THEMIS) onboard Mars Odyssey and highlight the key role of dust for the thermal behavior of the martian surface. OMEGA directly reveals for the first time some diurnal variations of apparent TI attributable to surface heterogeneities at macroscopic scale and enables to quantify these heterogeneities. In Nili Patera and Tharsis, local surface heterogeneities are modeled with layering and horizontal admixture of divergent slopes respectively. © 2014 Elsevier Inc.