Joint Omega - Themis Investigation of Tes Type Ii Deposits and Local Terrain

Introduction: Enhanced understanding of the mineralogy of the Martian surface can be achieved through joint analysis of the near-infrared and thermal datasets. Because the physical processes of absorption differ in these wavelength regimes, the joint datasets are complimentary and offer important insights into surface compositions and textures unattainable through independent and comparative analysis. Using an integrated dataset we investigate the central caldera of Syrtis Major, which is an advantageous location because of its mineralogic diversity as well as uniquely strong spectral signatures. We examine the spectral and geomorphologic characteristics of two TES Surface Type II deposits in this region, previously identified in [1], in the context of the local spectral diversity. Surface Type II is a global geologic unit identified within the TES dataset, and contrasting compositional interpretations of this unit imply very different surface evolution processes [2,3,4]. Because many previous investigations utilize the thermal emission dataset only, a detailed joint analysis of high-resolution OMEGA and THEMIS data can contribute important information. Dataset: At near global coverage, the OMEGA near-infrared imaging spectrometer on Mars Express operates with a 1.2 mrad IFOV and 352 spectral channels between 0.35 µm and 5.2 µm [5]. The spatial resolution varies from 300 meters/pixel at pericenter to 4.8 km/pixel at 4000 km altitude. With global coverage, the THEMIS thermal emission imaging spectrometer observes with nine spectral channels between 6.8 µm and 14.88 µm at ~100 km per pixel [6]. Background: This analysis combines data with the highest spectral resolution in the near-infrared (OMEGA) with the highest spatial resolution in the thermal infrared (THEMIS). Previous studies have taken advantage of the benefits of joint analysis [e.g. 7,8] noting enhanced mineralogic and textural interpretations. Prominent absorptions at VNIR (visible near-infrared) wavelengths are the result of charge transfers and electronic transitions while the TIR (thermal infrared) region is dominated by crystal lattice vibrations. Also, variations in grain size systematically affect spectral contrast and absorption band depth at VNIR and TIR wavelength regimes independently. Thus, a combined OMEGA-THEMIS dataset allows for a rigorous analysis of mineralogy and texture. Data from the TES instrument indicate the presence of two dominant surface mineralogies [2]. Deconvolutions of Surface Type I, whose type locale exists within the Syrtis Major region, indicate a basaltic