Unveiling Titan’s Mid-Latitude Surface Regions

Abstract:

Titan’s extended, dense, and hazy N₂-CH₄ dominated atmosphere shields its surface from direct optical observations except at certain frequencies where the methane absorption is weak. These “methane windows” are exploited by the VIMS instrument on Cassini. After accounting for the atmospheric contribution to the VIMS data, we use a Radiative Transfer code (RT) that includes the most recent evaluations of the aerosol and methane opacity characteristics [1;2] in order to simulate the spectra and to infer the surface properties as well as any possible evolution with time. We focus on some equatorial regions that have been identified as possibly subject to changes, having particular spectral properties and possibly being the strongest cryovolcanic candidate regions, that is: Sotra Patera, Hotei Regio and Tui Regio [3;4;5]. In addition, we examine some test cases and a vast expansion of terrain called the ‘Blandlands’, which are all not expected to change with time as confirmed by our results. The only changes with time we find are for Tui Regio darkening from 2005-2009 while Sotra Patera brightens from 2005-2006 at all wavelengths, indicating that dynamical processes control the regions, compatible with their complex morphology. We also use a despeckle filtering technique [6] on RADAR data in order to retrieve more revealing information on the morphology of these regions. We also associate radiometric and topographic data with the compositional information from VIMS to derive constraints on the chemical composition and the geology of the surface and the nature of these regions [5].

[1] Hirtzig, M., et al.: Icarus, 226, 470-486, 2013. [2] Solomonidou, A., et al.: JGR, accepted, 2014 [doi: 10.1002/2014JE004634]. [3] Lopes, R.M.C., et al.: JGR, 118, 416-435, 2013; [4] Moore, J.M., and Howard, A.D.: GRL, 37, L22205, 2010; [5] Solomonidou, A., et al.: in prep. (2014b); [6] Bratsolis, E., et al.: PSS, 61, 108-113, 2012.