Equatorial belt of Titan: Aaru region as seen by VIMS/Cassini

Abstract

Since eleven years of observation, near-infrared imaging data from Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini reveal a variety of surface units that are compositionally and structurally distinct. The analysis of these units enables constraining the surface composition of Titan, which is of prime importance for modeling Titan’s interior, surface, and atmosphere, particularly in the search for an endogenic methane source. For this study, we investigate a selection of units of interest seen in VIMS data by comparatively applying an empirical correction and a radiative transfer code in order to correct for atmospheric contributions and retrieve surface albedo. SAR swaths from the Radar instrument were also used for geomorphological mapping purposes. We focus on the region of Aaru, located in the equatorial belt and centered at 10˚N and 340˚W, where several geological features are have been identified: (1) infrared-brown dunes material; (2) a strongly eroded impact crater named Paxsi; (3) mountainous and infrared-bright terrains; and (4) infrared-blue areas devoid of dunes (similar to those seen in other regions probably enriched in water-ice, such as Chusuk Planitia). By using our radiative transfer model, we estimate the surface albedo of regions of our interest within different infrared units of the Aaru region and compare with spectra of surface candidates, starting with water-ice and tholins. As seen in the similar study over Sinlap crater and its surroundings, this method of analysis allows understanding of the compositional and structural relations between the different spectral units.